If your first reaction to “intermittent fasting with type 1 diabetes” is…”Oh my gosh, my blood sugar would be so low! I could never do that!” …then definitely keep reading.
In this guide, I will cover everything you need to know about intermittent fasting with type 1 diabetes:
Table of Contents
What’s the point of intermittent fasting?
There are 3 general reasons a person might want to pursue intermittent fasting.
- Weight-loss: This is the most obvious and most common reason to give it a try.
- Simplicity: Reducing the number of hours each day that you have to think about food, track food, make decisions around food, and cook food can be really freeing! Instead of frantically and unexpectedly skipping meals because of a hectic schedule, intermittent fasting allows you to properly and methodically skip eating during parts of the time.
- Energy: Once you get going, and you’re no longer freaking out about, “How hungry will I feel!?!”…this approach to eating can actually give you quite a boost of energy because your body will be burning fat for fuel instead of relying on sugar from your blood. Body fat is an endless source of energy.
Before we get started: if your blood sugar drops just because you don’t eat for a handful of hours, you’re taking too much background/basal insulin via pump or injection. Talk to your CDE or primary care doctor about “basal testing.” (Or check out Gary Scheiner’s book, ‘Think Like a Pancreas’ and do the basal testing yourself!)
Basal testing literally consists of purposefully skipping a meal (or two) in order to see if your insulin keeps your blood sugar steady, or if your blood sugar significantly rises or falls out of your personal goal range. If it rises, you’re not getting enough background/basal insulin. If it falls, then you’re clearly getting too much.
How intermittent fasting works
When you wake up with an in-range blood sugar (ideally between 70 to 130 mg/dL as a person with type 1 diabetes…the 130 mg/dL being on the higher end but offering some room for imperfection in a complex disease) and you don’t eat breakfast, which means you don’t take a bolus of insulin, your body will continue to burn fat for fuel because you have yet to introduce actual fuel. You have yet to turn on that switch telling your body to rely on glucose for fuel instead of fat.
The moment you eat or drink something containing calories, your body says, “Alright! Now it’s time to burn glucose!”
What an intermittent fasting schedule looks like
There are a lot of different ways you can approach fasting, and after doing this for several years on and off, I’ve found I can flexibly create my own approach that feels most natural to me.
Here are 3 of the most popular fasting schedules, adapted from Dr. John Berardi’s guide to intermittent fasting:
- 24-hour fast: You eat dinner on Thursday (for example), and then you don’t eat again until dinner on Friday. This should generally only be performed once per week. (Read Dr. Berardi’s guide to see what happens if you do a 24-hour fast too often.)
- 16-hour fast: You eat dinner on Thursday (for example), and then you don’t eat again until 1 or 2 p.m. the next day. It’s important to note that you should still eat a normal day’s worth of calories during that 8-hour eating window. If you’re trying to lose weight, that amount of calories might only be 1200 to 1600, but you still need to get your calories while following a fasting program.
- Periodic fast: You suddenly decide to go 24 hours without eating, unrelated to your fasting or eating schedule throughout the rest of week. I like using it when I know I’m going to be eating a really heavy meal (Thanksgiving, holidays, pizza or Chinese food, etc.). I’ve also used this when I know I’m going to be sitting in a car for a long time on a road-trip, or if I know I’m going to be somewhere new with my kids and I really don’t want to risk any low or high blood sugars – I just want to remove diabetes from the equation altogether so I’ll fast as long as I can that day.
If you search the web on intermittent fasting, you’ll find there are people who emphasize that fasting for weight-loss needs to coincide with very clean-eating and attention to nutrition, while you’ll find others who say they fast all day and then eat pizza every night.
If you’re trying to lose weight, you’ll really want to lean towards the clean-eating and attention to nutrition (with treat-days planned of course, for long-term success and adherence), but if you’re trying to maintain your weight, I think intermittent fasting offers a lot of wiggle-room for less healthy eating.
During the holidays, for example, I let my eating choices slide quite a bit compared to my normal routine, but I was still following a 16-hour or 24-hour fasting schedule most days of the week, so I didn’t actually gain weight beyond a little carb-laden bloating and water retention.
But won’t I be hungry?
Guess what, it’s okay to be a little hungry. After you stop freaking out about your belly not feeling full 24/7, and push through it around 10 a.m., you might actually notice that you feel a little bit awesome. A little more clear-headed, a little more focused, even a little more energy.
Drink some water – it’s good for you anyway – and embrace that feeling of your body just being empty. Yes, there are many ways to lose weight by eating every 3 to 4 hours, but that’s not the only way to eat, and it’s not the only way to lose weight.
Are you someone who is always thinking about their next meal? Always snacking?
As Dr. Berardi explains:
“Intermittent fasting can be helpful for in-shape people who want to really get lean without following conventional bodybuilding diets, or for anyone who needs to learn the difference between body hunger and mental hunger.”
But if you’re an athlete or intense exerciser...you might simply find that you really need that morning fuel because of your athletic pursuits! That’s okay! That just means intermittent fasting isn’t for you.
But isn’t eating breakfast really important?
Eating breakfast can absolutely be a crucial part of weight-loss and maintaining a healthy metabolism, but it’s not the only way, and more recent research has really diminished how important breakfast really is.
“There haven’t been any conclusive studies that found eating breakfast to have a positive effect on weight loss or weight maintenance,” explains sports nutritionist and registered dietician, Leslie Bonci, as reported in Popular Science.
Also, the idea that skipping breakfast causes weight gain is over-simplified and very false. It’s not the act of skipping breakfast that can cause weight gain, but that in those studies it’s observed that a large majority of those who skip breakfast also lack other healthy habits overall.
“It could be that eating breakfast is simply a marker of a healthy lifestyle and, in itself, doesn’t protect against obesity,” explains Science Alert.
“Several randomized trials (where people are randomly assigned to a certain behaviour, such as eating breakfast or skipping breakfast) have not found any evidence to suggest that skipping breakfast causes weight gain. Despite the association between skipping breakfast and weight gain, experiments specifically designed to try and establish cause and effect haven’t provided evidence that skipping breakfast causes you to put on weight.”
How to do intermittent fasting with type 1 diabetes
As a person with type 1 diabetes, you might even notice that you feel…a little free, because you aren’t worrying about whether you’re going to be high or low after your breakfast.
The awesome part of this for people with type 1 diabetes is this: your blood sugar is steady, steady, steady all morning long until you end your fast by eating at 11 a.m. or 2 p.m. or dinnertime…depending on which fasting schedule you follow.
I’ve also found that if I do a 24-hour fast before a carb-heavy meal like pizza, I’ve found that fasting actually cuts down significantly on the insulin I need for that meal.
If you stick to your fasting program consistently, you’ll find you lose weight and you gain insulin sensitivity, which means: you’ll need to decrease your background/basal insulin rates! This is a good thing! This is part of weight-loss with diabetes, but if you aren’t expecting it, you’ll be annoyed and frustrated with the low blood sugars.
How to adjust high or low blood sugar when fasting
Waking up with an in-range blood sugar is extremely helpful, but obviously, we’re not perfect and things happen. Here’s how to manage your plan for fasting if your blood sugar is not in your ideal range when you wake up:
- If you wake up a little high, sure, you can take a reduced correction dose (read ‘Think Like a Pancreas’ if you don’t know your own correction dose), and carry on with the fast, but introducing that bolus of insulin could be enough to switch on your body’s need to burn glucose for fuel. (For legitimate “dawn phenomenon” high blood sugars, you may simply need a bolus correction of insulin every morning that really is part of your “basal” insulin but is applied via pump or injection as a bolus. If this prevents morning fasting highs, it’s part of your fasting regimen!) *Read more about managing “dawn phenomenon” here.
- If you don’t take that correction dose of insulin, then you’re just spending the next several hours with a high blood sugar…which is counterproductive if our overall goal is health…right? So definitely take the insulin you need in order to be at healthy blood sugar levels–that’s your first priority.
- If you wake up low, then you obviously have to eat and fasting is no longer going to work. You’d be better off eating a healthy breakfast, fueling your metabolism since it’s already burning glucose for fuel, and trying again tomorrow.
- If you routinely wake up with blood sugars that are too high or too low, you need to go back and do some basal testing or test your insulin-to-carbohydrate ratios that you’re using for the food you eat before bed.
- Or this sneaky blood sugar problem: You need to stop binge-eating late at night. If you’re currently up at midnight eating yourself out of house and home, focus on this first before pursuing intermittent fasting. People often blame high blood sugars in the morning on “the dawn phenomenon” when it’s actually the result of late-night binge-eating.
It’s not a magic trick. It’s not a fad. It’s just basic science of how the body responds in a fasted environment.
Exercising in the Morning When Fasting…Is Actually Easier!
When you’re fasting during your exercise, your blood sugar isn’t going to burn up and drop–this is a good thing! Exercising while fasting (which means you did not just take a bolus of insulin for food or a high blood sugar) is easier because your body will burn body fat for fuel instead of glucose. I didn’t believe it either when I first learned this from the bodybuilders at my gym many years ago, but it works.
You will find that with weight-lifting or other anaerobic workouts, your blood sugar will possibly rise during a fasted workout, which means you might actually need a bolus of insulin for that type of workout. This will not take away from your fasted efforts, it simply helps use the glucose that’s being generated from the glycogen in your muscles being broken down due to your anaerobic workout!
I LOVE fasted cardio! In fact, I make sure that all of my exercise sessions happen either fasted in the morning or fasted in the evening (by not eating anything after 1 p.m. and then getting on the treadmill around 7 pm. This ensures that all bolused rapid-acting insulin is well out of my system. It works. When I used to lift weights, I did find that I needed 1 unit of insulin in the morning if I was doing a fasted weightlifting workout.
So in a nutshell:
- wake up with an in-range blood sugar (or correct a slight high with half of your usual correction)
- begin your workout while fasted
- check your blood sugar halfway through your workout during the first few experiments for safety’s sake
- if your anaerobic workout proves to raise your blood sugar, take half of what you would take to correct that high — but take it when you start exercising to prevent the high in the first place
- if your workout is aerobic (cardio), just continue your workout — you shouldn’t see a rise in blood sugar from aerobic fasted exercise
- check your blood sugar at the end
- shower (thank you)…and enjoy the rest of your fasting
Frequently Asked Questions
Is intermittent fasting safe for people with type 1 diabetes?
Absolutely! But you need to make sure your insulin doses and medications are properly tuned. For type 2s taking diabetes medications that intentionally lower blood sugar, you’ll likely want to talk to your doctor about taking that dose with your first meal versus “in the morning” if you intend to fast in the morning.
For type 1s, as discussed extensively above, your insulin doses should be finely tuned (even if you don’t ever plan to fast) so that you can miss meals and your blood sugar is generally steady and in a healthy range. Adjusting your insulin doses to meet this standard is called “basal testing.” If you’ve never done any basal testing to assess the accuracy of your personal insulin doses, definitely do that first. And do it even if you don’t ever intend to fast. It’s essential to diabetes management.
Again, as explained earlier, during your first week of fasting, check your blood sugar often during your fasting window to see how your body responds. And if you stick with it long-term, you’ll find you definitely will need to reduce your basal rates (even within a week or two) because intermittent fasting has an awesome benefit of…increasing your sensitivity to insulin!
What can you drink during intermittent fasting?
During the time-frame that you’re not eating calories, you shouldn’t be drinking any calories either. Black coffee or tea or water or seltzer (or diet soda, if you must) are all safe to drink. In general, I don’t encourage the consumption of drinks loaded with fake sweeteners. Drinks like Vitamin Water, even the sugar-free version, still contains calories. Read your labels carefully, and if all else fails, ditch the “diet” products for some all natural, chemical-free plain water!
Do you need to do intermittent fasting if you already follow a ketogenic diet?
You’re obviously going to be burning more fat than the rest of us after eating a ketogenic breakfast, but even some of that breakfast will be converted to glucose and require a bit of insulin to digest, so intermittent fasting still applies to keto-folks, too.
Adding fasting to an already disciplined ketogenic diet will definitely help your weight-loss progress.
Just beware, however, that if you don’t already understand how to eat enough on a ketogenic diet, adding fasting to the mix can be a recipe for a binge.
I highly recommend studying and practicing ketogenic eating for a few months before adding fasting to it. It’s very common for new low-carb eaters to eat too little because they are still afraid of eating too much fat. And fat, as you’ve probably heard, is a pretty crucial part of a successful ketogenic diet!
Why I love intermittent fasting as a mom
I can wake up in the morning, drink a cup of black coffee and guzzle some regular ol’ water, then pack our bags and head out the door to the playground or playgroup or the library. I can chase my kids around all morning long and I don’t have to worry about my blood sugar.
If I woke up at 90 mg/dL, I know my blood sugar is still in that zone.
I didn’t have to spend any time making my own breakfast. Or trying to find the time to make my own breakfast. I don’t have to worry about getting real, healthy food into my own belly until we come home from our morning activity, and I get the kids lunch and get everybody settled.
(If you’re not a mom of two children, let me tell you that finding time for your own breakfast is actually incredibly challenging some days amongst the diaper changes and the bottles and playtime and the…on and on and on! When that second kid pops out, parenting is ON in full-power-mode 24/7.)
By 1 or 2 p.m., I’m not starving, I actually feel pretty energized after that morning fast. And making myself a healthy meal feels very doable because the busiest part of the day is behind us.
Should you try intermittent fasting?
If all of the above sounds appealing to you, give it a try!
A few things to keep in mind when trying intermittent fasting with type 1 diabetes:
- Do you currently have a healthy relationship with food? If not, I would address that first. Fasting is not ideal for the yo-yo dieter or someone trying to recover from an eating disorder. Visit We Are Diabetes or check out my book on Emotional Eating with Diabetes or Diabetes Burnout to get started.
- Take good notes! The first week you try fasting, write down the insulin you took before bed, what your blood sugar was in the a.m., etc., so you can pinpoint any diabetes-related variables that are causing lows or highs in your blood sugar during the fasting period. For example: if you’re still up at midnight eating chips and ice cream, you can absolutely bet that will raise your blood sugar during the hours of 6 a.m. to 12 p.m. when you’re fasting. Some people blame dawn phenomenon for what is actually late-night binge-eating.
- During the first few fasts, check your blood sugar often. Even though fasting itself shouldn’t cause low blood sugars, your insulin doses simply might not be accurate! And nothing will reveal that sooner than fasting. Check your blood sugar often and take good notes. Learning how to study and adjust your insulin doses is a crucial part, I believe, of long-term success in life with type 1 diabetes.
- It doesn’t have to be 100% to benefit you: If I wake up and feel really hungry and genuinely feel an intense need to eat, then I listen to my body, and I eat breakfast. If I want to go out to breakfast (once in a blue moon) with my family, then I eat breakfast. It’s not a big deal! Make it work for you. Follow the program as much as you can, and don’t freak out when life gets in the way.
- You may find it useful for a few months, then back to a normal schedule. I’ve found that intermittent fasting has been really wonderful for me for several months at a time. And then I take a break from it for a couple of months, and then I naturally feel ready to follow that schedule again. Listen to your body and find what works for you.
- Be patient. If you fail a day of fasting because you gave in and ate one of those goddamned office muffins, relax. I’m a big believer that creating your own life around nutrition is a very long work in progress. Be constantly open to evolving, learning, trying new things, and never never never shaming yourself for being imperfect. It’s one big science project. Enjoy the project, stop punishing yourself, and learn to love the food you eat. Food can be fun, even when you’re trying to lose weight!
Learn. Study. Experiment. Repeat!
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Great article! Thank you very much for writing this.
I’ve been a T1 for almost 30 years (pump user). In overall good health and very active. I’m 36 yrs old, and could afford to lose another 10- 15 lbs. Intermittent fasting has intrigued me for several months now and I have very good results, while not exercising.
I have several questions.
1) Whats your opinion on the need for protein post workout (aerobic or anaerobic) ? And if you are pro protein consumption post workout what do you recommend to eat?
2) How do you recommend keeping sugars up during Aerobic activity? Anything besides reducing basal rates?
Best, Jack Berger
Generally, most of the recent research indicates that you don’t have to eat protein right after your workout. What’s more important is your overall daily protein intake. If you decide to fuel right after a workout any lean protein combined with a relatively fast-acting carbohydrate will do (whey protein and apple or chicken and rice are both good options). I’d skip the fat since that will slow down the release for the nutrition.
As for maintaining optimal BGs during workouts, there are really only two levers to pull, insulin or carbohydrates. When it comes to insulin you can reduce basal or bolus. But another trick is to use your hormones to your advantage. If you tend to see a rise in the AM (Dawn or Feet on the floor) you can plan your workout during that time. If intervals tend to make your BGs rise, include a few of those up front during your workout.
Hi! I have been a type1 dm for 22yrs, and my blood sugar readings are mostly erratic. I seem to be very sensitive to any addl carb, even something like 2 slices of bread instead of just 1 will send me spiking. But i am curious about intermittent fasting as it sounds like the most flexible diet i can take on for long term. My current setup is 13u Lantus (basal) in the morning then 2-4u Apidra (bolus) every meal/3x a day. If i take on the 16hr plan (dinner today until lunch tom), 2 questions:
1, Do i still inject basal in the morning? (I’m supposing i still should, asking anyway to be sure :P)
2, I suppose i will be skipping the morning bolus?
TIA! Your article has been very informative to me, both in fasting and in glucose/insulin interaction 🙂
Hi Slaxx!!!
Thanks for your in-depth question! A few thoughts for you:
1. If eating two slices of bread WITH a bolus of insulin sends your blood sugar raging, I would really recommend that before pursuing intermittent fasting, you get your insulin doses in tune by learning about your Insulin-to-Carb ratio (ICR), as well as doing some basal testing. (Definitely get yourself a copy of Gary Scheiner’s “Think Like a Pancreas” on Amazon! A must-read for all type 1s.
The reason I’m suggesting this is that if you take a dose of 2 to 4 units of insulin at every meal, that sounds to me like your doctor never taught you about ICRs. Your ICR is the amount of carbohydrates ONE unit of insulin can cover. Personally, for example, my ICR is usually 1:15. At a different time in my life, my ICR was 1:10. It can change as your sensitivity to insulin changes.
The basal testing is critical because it ensures that your background insulin dose is accurate. For example, there was YEARS of my life where I needed 30 units of Lantus (when I was chubby and not active in early college), then it went down to 20 units when I was powerlifting, and then today it’s at 9 units because I”m the leanest and thus most sensitive to insulin that I’ve ever been.
Ensuring that your background insulin dose is accurate will also impact what your blood sugar does around meals, even though we think of our bolus insulin as the insulin we take to cover our food. Both are critical for blood sugar management all day long.
2. YES, if you pursue intermittent fasting, you would still take your basal/background insulin but you would NOT take your meal-bolus because you aren’t eating those carbs. If you wake up with a high blood sugar, you would use your CF (correction factor) to determine how much insulin you need to correct that high and then carry on with your fasting.
Let me know what questions this brings up!
Thank you for the reply, exactly the facts I need to know. Indeed, my doctor has not taught me about ICR checking, though she did tell me that maybe i should start carb counting. I guess i’ll have to practice both now to calculate my doses better.
One last thing (for now? Lol), are the effects of IF immediate with sugar levels? Like, compared to keto, i heard it takes at least a week to see changes/feel effects. With IF, do you observe changes the next day? Lows or highs/as per insulin intake?
So grateful to read this tonight! My daughter is almost 15 and has had T1D since she was 3. In the past 2 1/2 years she has gained 40 pounds and she is incredibly frustrated. She is such a beautiful girl and wants to shed some weight and came across intermittent fasting. When I was her age, I was diagnosed with Hashimoto’s Disease and so my metabolism became extremely sluggish. I thought possibly this was the case for her but it isn’t.
Is there any advice for a young lady who is trying IF? Her endo just warned her to stop putting on weight. That was about it. She plays volleyball everyday; this is her daily exercise. Th
Thank you so much for any advice! (The only advice I have received so far was that I should never ever tell a 14 year old to diet. As a mom, I love my daughter too much to not be honest with her. I want her to be healthy. It’s not about being skinny – it’s about taking care of herself.)
Thank you again!
Hi Sarah!
Ohhh how very frustrating for your daughter! I too gained weight in my early high school years and I feel certain it was diabetes-related just because we are battling blood sugars, teen hormones (which lead to insulin resistance), and having to deal with diabetes as a teen is just not ideal!
My first question would be: what is her diet/nutrition like? Before venturing into IF, I’d recommend she first start looking at her current eating habits. How much of her diet consists of cafeteria grilled cheese or bagels? (Common teenager food!) A typical teenager diet for a type 1 will lead to weight-gain faster because we are taking a synthetic version of a hormone and we simply need more of it to equal the job of real human insulin.
If there’s room to improve her overall nutrition (again before trying IF), I’d recommend focusing not really on carb intake (because she is a growing teen) but on “Is this real, whole food? Or is it really processed?”
A lunch of apple, nuts, carrots and hummus vs. grilled cheese.
A dinner of meat and sauteed veggies vs. mac n cheese.
A snack of grapes and cheese.
A breakfast of eggs and whole oats (in the microwave still if you prefer!) with frozen blueberries!
The reason I wouldn’t recommend first going towards IF is because: She is a growing teen and being a student without food until 1pm is definitely going to impair her ability to think and focus at school!
I would also ask: how are her blood sugars? Weight-gain in type 1 diabetes can also be the result of constantly having to correct highs. If that’s the case, she may need to fine-tune her basal insulin (check out the book “Think Like a Pancreas” for help there or work directly with Jennifer Smith CDE/T1D via Skype at IntegratedDiabetes.com. She’s awesome and helps T1Ds with weight-loss and BG management).
Let me know if this is helpful!
Hi Ginger!
I am so happy I found this website!! My case is similar, I’m celiac and I’ve been diagnosed diabetes type 1 this January. The thing is that nowadays I’m controlling the disease doing a low carbohydrate diet and lot of exercise as my doctor saw that I could keep it without using insulin. I knew about the intermittent fasting because my brother (who is biologist and is into sport an diets) started doing it, and he told me that it could work for me, to lower my sugar in blood. The question is the next: during my day I am able to control better my sugar in blood because I’m active and I exercise almost every day and in the morning is when I mostly have higher measurement. What do you think about trying intermittent fasting on dinners to lower my sugar in blood during my sleep hours?
Thank you in advance for your response, and I’m looking forward to it.
PS: keep it up this work, it’s amazing!
HI Borja!
I’ve met an adult T1 diagnosis like you who was able to delay going on insulin for a couple years by eating no-carbs! Incredible! Takes a lot of discipline.
While I’m definitely no expert on your unique early-T1 position, the short answer is that completely unrelated to fasting, simply exercising in the evening will ABSOLUTELY cause you to be more insulin sensitive while you’re sleeping and should lower your blood sugars. You don’t need to fast in order for this to happen.
That being said, you could “start” your fast around 3pm (or whenever), not eat dinner, not eat all night, and end your fast in the morning when you eat breakfast. But again, I really think you’d get plenty of insulin sensitivity just by moving your exercise routine to the evening to tackle the time of day when you’re seeing your blood sugars at their highest.
Unfortunately, no matter how few carbs you eat, you will eventually need to go on insulin. It’s inevitable if you’ve been tested for the auto-antibodies that indicate type 1 diabetes vs. type 2 in an adult onset case like yourself. And hey, as someone who has been taking injections of insulin for 20 years, I gotta say I’d much rather take injections than be limited to a diet that allows ZERO fruits or dessert! Being on insulin isn’t such a bad thing if you have type 1 diabetes…it gives your life–and your plate–variety! 🙂
Wishing you the best. Hope this is helpful — holler back if you have more questions!
Thanks for the article, really interesting stuff that I have never thought about and I have been a type 1 diabetic for 16 years. I have an insulin pump and have been on one for 11 years. Ever since having an insulin pump, whenever I exercise I always suspend and disconnect my pump. Do you guys usually exercise with it on so that you still get your basal during exercise? I play ice hockey and I am a goalkeeper in soccer and I always felt like I would fall on my pump and literally crush it haha (from getting hit in hockey or diving as a goalie). What I usually do is check my blood sugar in between periods/halftime and do a bolus correction. My question is how does this impact IF as I am not eating anything, but I am giving a bolus rather than my usual basal causing my blood sugars to fluctuate a bit more. I also test my blood sugar before games and correct depending (ice hockey is so vigorous of an exercise I find my blood sugars going low all of the time). I find it interesting that you say that if you have a correct basal then your blood sugars shouldn’t dip with exercise but that has always been the case with me for ice hockey. However, in thinking more about it I usually always ate a little something before hockey for energy and I would also bolus usually not the total amount of carbs but for some and so maybe what is happening is while playing that bolus is more impactful whereas if I fast well before the game and just basal then my blood sugar wouldn’t go low? I’ll be interested to see your thoughts. Thanks!
Hi Kyle!
Let me try to answer your questions fully hear but please holler back again if I didn’t address it fully:
1. I don’t use a pump, but there are many ways a person on a pump can approach exercise/insulin management.
A) If you’re going to disconnect, and it’s the middle of the day, you’ve been eating etc. the only big flaw with this is that several hours later your BG can go up because that basal from two hours of exercise isn’t in your bloodstream. And remember, basal insulin has about a 4-hour window of impacting your BG after it’s dosed.
B) If you’re fasting and your basal rates are correct, you should be able to play hockey without a drop in your blood sugar. If you see a RISE in your blood sugar, that’s because hockey is intense, and could be a mix of anaerobic (short bursts of intense skating, like a sprint, over and over) and the overall aggression of the game. If this is the case for you, personally, I took 1 unit of insulin BEFORE weightlifting in the AM when fasted to prevent a spike from anaerobic exercise.
C) If you can’t leave your pump on because you’re afraid it’s gonna get smashed, that’s definitely a worthy reason to take it off. However, that should only make fasting even easier. If you start out the morning with a safe/healthy BG, take your pump off, play hockey (and you’ve established you don’t need a bolus for reason B), your BG should definitely stay steady during your workout. If it drops, then you’re likely getting too much basal in the hours before you disconnected from your pump.
Let me know if that addresses everything!
Ginger
So I’m very interested in IF because I’ve seen people (without diabetes) have success for fat loss while doing it. However I have a couple questions…
1. To clarify, if I were to wake up at, let’s say, midnight or 1 am or 2 am with low blood sugar and I corrected for that, I would then need to eat breakfast because my fast would be interrupted. Correct?
2. I’ve heard so many times that not eating breakfast will actually cause your body to store fat when it doesn’t get breakfast. So, if I have nights where I have to interrupt my fast because of low blood sugar which causes me to eat breakfast, and therefore I’m not being consistent with IF, would that cause me to gain weight (or just not lose fat)? Or is IF not about being consistent is it’s really just burning fat via fasting on the days that we can?
I actually just purchased Think Like A Pancreas (thanks to reading this article) and I couldn’t put it down last night! So I am going to do some test nights to make sure I don’t need to adjust my basal insulin, and that may prevent lows in the middle of the night. BUT, they still happen whether we like it or not some times and I want to make sure IF won’t actually cause me to back-track in fat loss due to the complications that go along with our diabetes.
Thanks so much! I found this article super helpful and have bookmarked this website for future reading 🙂
– Shelby
Hi Shelby! Okay so…
1. If you had to treat a low at 2 am, but you were still up for fasting when you woke up for your day, your fast would simply have started after 2 am instead of at your earlier bedtime. Is it perfect? No. But is it still a fast if you don’t eat again until 1pm? Yes. As mentioned in responses to earlier comments, try not to get too caught up in it being perfect. Diabetes is gonna make this inevitably trickier because, as you’ve pointed out, sometimes we HAVE to eat.
1.a. On a personal note that might be helpful to you: I used to have lows CONSTANTLY at 2 am. I learned that in people who are fairly sensitive to insulin, Lantus insulin has a noticeable peak about 5 hours after injecting it. For me, that was clearly around 2 am. I’d go low every night unless I started the night a little high. The fix? Switching to Tresiba insulin! It’s awesome — so much smoother and no peak at 2 am so I can go to bed with a BG of 100 mg/dL and wake up around 100 mg/dL.
1.b. If you’re on an insulin pump and the above story is totally useless for you, definitely take a look at your basal rates with the help of your CDE etc. to get them fine-tuned. You’re going low because you’re either getting too much insulin with the last meal you ate or you’re getting too much basal. (Gary’s book that you now own, Think Like a Pancreas, talks about this too!)
2. The idea that skipping breakfast makes you fat is very outdated and based on very incomplete data. In a nutshell, it was based on the people who skip breakfast and then binge-eat later in the day on crappy food. It’s not the “skipping breakfast” part that leads to weight-gain, it’s the compensating by binge-eating a lot of very poor quality food. The same goes with “it’s bad to eat late at night”…well, no, it isn’t. If you’re eating 2000 calories in one sitting at the end of the day and those calories are also made-up largely of pizza, fries and cupcakes, then yeah, that’s pretty bad. BUT if you’re eating real food, WHOLE food, and are in control of what you’re doing and NEED those calories to meet your basic calorie needs, then eating at night is just part of your schedule.
If you Google search “Why skipping breakfast doesn’t lead to weight-gain” you’ll find very recent studies disproving that very outdated theory!
In the end: intermittent fasting with a diet that consists MOSTLY of whole, real food is going to be a great thing for most people. If your diet currently consists of a lot of processed junk or fast-food, I would consider focusing FIRST on improving the quality of what you’re eating (learning to cook more too, etc.) and SECOND adding in fun things like IF when you’re ready.
I see! Well I appreciate the help and response. Thank so much! That definitely cleared things up for me
Thanks for all your information. I have been trying IF now for a few weeks. I have always feared that Bolus corrections (1-3 units typically) would kick me out of a fasting state. Based on some of your replies, that seems to be incorrect? I have been trying to correct any fasting highs with temporary rates on my pump (150%-200%) for an hour or two, in order to slowly introduce more insulin without a spike. Obviously, this keeps me higher for a longer period of time. Apparently, this has been unnecessary?
Hi Chris!
In an ideal world, we wouldn’t take a bolus of insulin when we’re trying to fast. But personally, my FIRST priority is managing my diabetes properly and keeping my blood sugars in a healthy range for as much of the day as I possibly can. Intermittent Fasting comes second. If my diabetes demands that I need a bolus of insulin when I’m fasting, then I take it. The fasting won’t be quite as perfect, but the bigger picture is my HEALTH, not my ability to fast. It’s up to you, but I personally would recommend taking the bolus to correct your high blood sugar.
Hi – T1 diabetic for 35 years – have started doing IF about 4 weeks ago – so far it’s working great. However, I sometimes struggle to get all my calories in from 12-8pm, so I often slip to eating till 9:30pm which then pushes my fast till 1:30PM and then rinse and repeat…
My question is this: “If you wake up a little high, sure, you can take a reduced correction dose (read ‘Think Like a Pancreas’ if you don’t know your own correction dose), and carry on with the fast, but introducing that bolus of insulin could be enough to switch on your body’s need to burn glucose for fuel.
I am confused about this – because I don’t have DF, but what I do have is the “get out of bed, body gets cranking and I just spike up to 200 from a comfortable 130”. As such, I bolus as soon as I wake up, which keeps at around 145 (which according to my endo, is what I should be aiming for). My question is if I bolus, how does my body “switch on” to wanting to burn glucose for fuel – does this mean it’s breaking down my muscle?
Hi Antoine!
Okay, so, first of all: I think if your endo has you aiming for 145 mg/dL as your fasting basal rate, you need a new endo and a slight increase in your basal insulin. Unless of course there is a medically logical reason he/she is limiting you to a fasting BG of 145 mg/dL. Many endos simply don’t realize that today’s insulin and technology easily enables us to fast at a more non-diabetic number!
I would guess that with a slight increase of 1 to 2 units total in your daily basal insulin dose, you might even find that morning spike from 130 to 200 mg/dL goes away.
However, if it persists when you’re waking up at 100 mg/dL and you find yourself at 180 mg/dL, etc. and you of course need to take a slight bolus for that, you should. And you shouldn’t worry about switching to burning glucose because that morning spike is likely the result of hormones, not food. If your pancreas was doing its job properly, it would be letting out a bolus of insulin to compensate for those hormones, too.
I also wouldn’t stress so much about making sure you’re doing a perfect 16:8 fast. If you need to eat at 9:30pm to get your calories in, go for it. If fasting until 1:30 feels like too much of a stretch, listen to your body and start eating at 12:30 or 1pm. There is no hard and fast “you must do it this way for results.” Listen to your body, definitely make sure you get the calories you need in your eating window, and keep your eyes on the big picture rather than the tedious details. It sounds to me like you’re ROCKING it at fasting, and at diabetes management in general! Let go a little bit of thinking it needs to be perfect in every way, and enjoy the process.
Hi! I, like many t1s, struggle with weight loss and would like to give this a try. I’m anxious about ketones though. I often find that I start seeing ketones in my urine if I go without eating for more than a few hours, especially in the morning. Moving away from a low-carb diet has helped with this, but I’m still nervous about it. I also struggle with a lot of nausea, which often coincides with the ketones. Do you have any experience with these issues?
Hi Bella!
Starvation ketones and diabetic ketoCidosis ketones are two very different things. Many of us (even non-diabetics) actually wake up with mild ketones just from fasting while we sleep. Pregnant type 1 women wake up with mild ketones every morning!
DKA is when ketone levels are over 20 (dark dark purple if using urine versus a ketone blood meter.
Ketones from a ketogenic diet or fasting aren’t going to be much higher than 5 if you’re lucky!
Ketones on their own are not a harmful thing at all. That’s what ketogenic diets thrive on. The only time ketones are dangerous is when your body is flooded with them and too little insulin is present to properly use blood glucose for fuel, which goes hand in hand with persistent high blood sugars.
So in a nutshell: any ketones you experience from fasting are actually a GOOD thing as long as they are not the result of 300+ blood sugar levels. Ketones from fasting are IDEAL and are the direct result of fasted weight loss!
Leave your worries behind and give it a try!
Hi. I’m trying to do If from 10-6 every day.
Type 1 diabetic. My question. If I go low and drink juice does that mean my fast is “wasted “ and should start again tmw? Also – I’m doing hiit three x a week and cutting Carbs but really don’t see Weight loss or my strength Improving. Still get tired. My eating is a bit all over the place so that could be why. However I’ve seen people “starve “ themselves and loose Weight. Why isn’t that the case for me? What is the best way to eat to loose Weight ( keeping in mind I do hiit and am ok w doing hiit)? Also is it effective to just do
If a few times a week and still see results ?
It’s fairly individual what weight loss regime works for different people, but most important is that it has to be something you can stick with. There is no magic plan except for being in a (reasonable) calorie deficit and sticking with it. Many don’t see any significant results until 3-4 weeks in, it’s about consistency and not jumping from one plan to the next. Just because you fast doesn’t mean you’ll lose fat. Try tracking what you eat during you “eating” hours and make adjustments based on that. If you’d like to read more about losing fat with T1D check out a detailed guide HERE
Bella! Just to add to Christel’s response. Yes drinking juice means your fasted program for that day comes to an end because you’ll definitely be burning glucose for fuel after that. But that’s just life with type 1. It happens. I try to brush it off and do my best to make it work the next day!
By what percentage should one reduce their long acting insulin? And which doses? I would be fasting from morning til dinner time?
That will really depend on your sensitivity and current usage. Dosing isn’t something we can advise on, but start conservatively (to be safe) and optimally work it out in collaboration with your medical team
Interesting read! I do have a question regarding how the body will use/transfer fat for fuel. In my understanding the body requires insulin to be able to use glucose as fuel (if not then you spike) so my question is if insulin is needed to use glucose as fuel is insulin NOT needed in the body to use fat as fuel? How do fatty acids get into your muscles for fuel w/o insulin?
Hi Daniel!
We all need insulin in our bodies 24/7 in order to survive. That’s your basal insulin in your pump OR your injection of long-acting insulin (Lantus, Tresiba, Levemir, Toujeo, etc.)
Fasting works because when you haven’t eaten in 8+ hours, and you continue to not eat, that means you aren’t taking a BOLUS (vs. basal) of insulin to cover the carbs/fat/protein in the food you’re eating. The moment you eat and take the insulin necessary to use that food for fuel or store excess as body fat/glycogen, your body is now burning primarily glucose for fuel, including when you’re performing cardio exercise. If you DON’T eat breakfast and you continue your fast (having not eaten since the night before), your body is burning body fat primarily for fuel but you do still have your basal/background insulin working to keep your blood sugars stable.
Let me know if that clears this up for you. I can assure you I didn’t come up with this theory/science on my own. It’s well established in the physiology of the human body. Fasted exercise has been used by athletes in the bodybuilding world for decades and decades because it so easily targets body fat for fuel.
Holler back with any questions!
Hi! I have done if for 10 days and out of them i worked out 7 days. I didn’t lose any weight even on 1300 calories. Could it be because I take long acting insulin morning and night ?
Hi Elly – weightloss is not linear and you can’t necessarily expect a large fat loss in only one week. A lot could be going on, you might be eating too little or not the right combination of things, you could have gained water weight, muscle etc. You’ll only gain weight from insulin (even morning and night) if you take too much and need to eat additional calories to keep your blood sugar up
Hi! I’m just now starting to read about intermittent fasting. I’ve read that 16 hour fast and an 8 hour eating period is ideal. Obviously as type 1, you can’t go 16 hours without insulin. I’m going to try fasting breakfast & mid morning snack and then take my insulin (fast acting & basal). Is that basically what you’re saying? Is there any benefit if you do the 16 hour fast/8 hour eating period, even if you have to take your basal insluin? What fat loss benefits are there for only fasting breakfast before taking insulin for the day?
Hi Jessica!
Fasting doesn’t mean you’re without insulin. You should still be taking your long-acting insulin or your basal insulin via a pump as normal. If your blood sugar drops low during your fast, that means you’re getting far too much basal insulin. In diabetes world, this is actually a purposeful “basal test”…
http://integrateddiabetes.com/basal-testing/
Ideally, a 16/8 hour fast is ideal if you eat dinner as usual. Go to bed. Wake up the next morning and don’t eat until 1pm. You would still continue your basal insulin per usual. So you would eat your breakfast meal at 1pm.
Does that make sense?
Does it matter if you take your basal insulin in the morning even though you are fasting?
No, you should still take your insulin. If it’s titrated correctly you shouldn’t go low/high despite doing IF
I’m so excited to find your site!
I’m a T1D for 32 years, pump/CGM user and self adjust/micro-manage basal/ratios etc. The ONLY time I’ve ever been able to lose weight was when breastfeeding and when I stopped eating for 2 weeks, due to pain from a undiagnosed gluten sensitivity. Anyway, I eat around 900 cal/day and still cannot lose weight. Even if I sleep all day, wouldn’t 900 calories be enough of a deficit to lose weight?? I do lose weight and become more insulin sensitive when fasting 18 hours but as soon as I eat the weight comes right back. I think it is WAY more difficult for me than other people with or without diabetes.
Also, I drop 30-40 mg/dl when walking 30 min. Are you saying that my basal is too high, if I can’t exercise without a drop in BG? A well known author and blogger with diabetes also recommends walking to reduce BG in T1D’s immediately following meals. Are you saying that is incorrect and that it only has to do with basal? Should I be able to do any activity without decreasing my BG?
Also, I would love your take on all those changes in basal requirements, like hormones etc.
Thank you and I appreciate all of your helpful information!
Hi Krissy – glad you like the site!
My guess is that your body is in complete starvation mode and unless you slowly increase your calorie this weight management will only become harder for you going forward. I’d suggest what we call reverse-dieting, slowly adding back more calories to not gain a lot of fat. And then you can start leaning out again. Might take some time to fix.
As for the basal question. Yes, if you’re fasting and walking makes you drop (and you don’t want it to) your basal needs to be reduced. That being said if you’re running high or have your AM hormones pushing your BG up, walking could be a great way to get it down.
As for basal requirements throughout your cycle you might need more insulin mid-cycle and end-cycle simply because your estrogen levels are higher at that time which makes you more insulin resistant
Hi Krissy!
In addition to all of Christel’s great responses above, I just wanted to offer a couple things to keep in mind:
1. There are A LOT ways I could try to lose weight that wouldn’t work well for me. But there are a couple that I know do work for me. My point is that what you’ve done in the past clearly hasn’t work for you …so what have you NOT tried? We tend to go back to our same ideas and efforts even when they don’t work if that’s the best idea we have for the issue. Working with someone like Christel and really getting your metabolism and nutrition finely tuned by someone with an outside perspective and some new ideas for you might be really, really worth it!
2. Like Christel said, your body wasn’t losing weight on 900/calories a day because that is WAY too low. When we deprive our bodies that severely of calories, they go into “starvation mode” and cling to every ounce of fat on the body, and absorb every calorie you eat. Fueling your metabolism to WANT to burn off extra fat is a bit of an art — and it’s something Christel excels at teaching people. But most of all it shouldn’t involve eating below 1200 calories at a MINIMUM.
3. Yes, your basal rates are definitely too high if walking on an empty stomach first thing in the morning drops your BG by 50 pounds. BUT if you’re talking about walking after lunch and after taking some insulin for a meal, then no, it makes sense that your BG is dropping. Highly recommend the book “Diabetes Athlete” by Sheri Colberg for better learning how to balance your BG around exercise OR working with Christel!
So again, I just want to ask: what have you NOT tried yet?
And what have you already tried that you know does NOT work for you?
Curious. I’ve been “skipping” breakfast here and there for a while. It helps me enjoy meals with my family more, but I was worried it was bad for me (Breakfast is the most important meal of the day!) Hoping to learn more about intermittent fasting as a type 1 diabetic for weight loss. THANK YOU for the great article!
If I drink water and green tea with stevia throughout the morning, does that count as fasting? Does the artificial sweetner affect the fast? What about a coke zero?
Also inquisitive about medication…like thyroid pill first thing in the morning with water?
Probably will be dependent on individual, but I was just curious if you have any insight or can direct me to more information. Thank you.
Hi Kristin,
Good questions and glad you found Ginger’s article helpful. Water, tea and coffee (or coke zero) won’t break your fast.
Skipping breakfast is only really bad if it leads you to make less optimal food choices the rest of the day.
I really want to say thank you so much. I
Have been doing keto for quite a while. And have fasted a few times. I haven’t been sure about it being safe with me being TD1. Thank you sooo much. The freedom is great. I do not like the one meal a day fasting. Honestly I’m not hungry so that is easy to do but getting my veggies in is important to me.
Wanda! Thank you for reading, and for your comment. I didn’t used to like the one meal a day fasting — it felt like a struggle to wait that long to eat…and then I did it several times by accident because of crazy days with 2 little kids…and I kind of like it now. Good thing there are a variety of approaches we can choose from!
I like to do an hour of a spinning class in the morning without eating breakfast, but I have to eat aprox. 8 glucose tablets during the class. I only take 8 units of basal before nighttime. Would you say that when I know that I’ll do a morning spinning class, I should lover my basal to eg. 4 units.
My question is then: What about the rest of the day? If I eat normally, will I not be in need of my basal then?
Another question: I thought that muscles needed the glucose in order to do a good exercise – isn’t that so?
Hi Helle!
1. Your body is VERY capable of producing glucose fuel without eating carbs — by turning protein in glucose. But the entire point of ketogenic and low-carb dieting (and the same logic applies to fasting) is that your body is burning body fat for fuel instead of just the food you eat. If your body required food every time you exercise, that would mean your body never burns fat during exercise…which we already know isn’t true. By fasting before you exercise, you’re helping to ensure that your body is burning fat for fuel instead of the glucose in your bloodstream! THat’s why it’s so great.
2. Regarding your blood sugar dropping during your spinning class. Let me start by stating: I am not your CDE. 🙂 Now that that is out of the way….if I were you…it sounds like you’re actually taking too much basal. You really shouldn’t need to feed morning cardio if you wake up with an in-range blood sugar and you aren’t taking any injections of fast-acting insulin. Again, if I were you…I would try reducing my basal dose by 2 units…and then see what happens. (I say two units because in generally it’s really advised to only make adjustments in insulin doses by 1-3 units maximum…since you are clearly very sensitive to insulin, 2 would be your maximum.) Let me know how this sounds to you. If you’re worried about going low, even after making a decrease, you could have a few glucose tabs…and if you’re high during/after your spin-class, then you know you can probably skip the glucose next time.
I’ll check back to see any replies you leave so please holler back with questions and results!
p.s. Helle, I wonder if you may find that with only 6 units basal, you could simply increase the insulin you take for meals just slightly to compensate…allowing you to properly fast in the AM, because again, your basal insulin on its own should not cause low blood sugars if you’re in a fasted state.
And lastly, what kind of long-acting insulin are you taking? For people who are very sensitive to insulin (which you clearly are based on your small dose), Lantus insulin can be troublesome because it actually starts to “peak” about 5 to 6 hours after being injected. This was a HUGE problem for me. My blood sugar would plummet every night at 3-4 a.m. I switched to Tresiba insulin, which is much more reliably steady! https://www.ontrackdiabetes.com/type-1-diabetes/3-reasons-why-i-love-tresiba-insulin-have-no-regrets
I’m a type 1 and take 33 units of Lantus now Basaglar in morning and 2 metformin in the morning and 2 more with dinner along with a small amount of short acting insulin as needed. Since I’ve been attempting a more keto friendly diet I have only need 2-3 units of short acting insulin at dinner. My problem is I drop dangerously low in the the early hours of the morning no matter how much I reduce my new Basaglar (same as Lantus). My GP keeps blaming it on me stacking but how could 3 units of fast acting insulin just once at 6 PM possibly be stacking? Needless to say I can’t lose an ounce with all these lows. I just picked up a two month supply of the new Basaglar, insurance made me switch but had the same problem with Lantus. I can’t afford to throw out my insulin, do you have any suggestions as it appears you experienced the same problem? I test before going to bed and if the number is as high as 150 I have to take juice and I still wake up at 40 or 50. I’m beyond frustrated, not to mention tired.
Cheryl!
I would guess the culprit is LANTUS!!! I switched to Tresiba because people with type 1 who are fairly sensitive to insulin will see a peak in Lantus efficacy after 5 or so hours. Check out Tresiba! I wrote more about this issue here: https://www.ontrackdiabetes.com/type-1-diabetes/3-reasons-why-i-love-tresiba-insulin-have-no-regrets
You never spoke about exercising in the am during your fast?
What’s the best way for a type 1 to do this without having crashing blood sugars?
I’m very interested in IF as a type 1 I never knew how to do it safely
Once you outline how to exercise on IF I’ll be good to go!
Kim! How incredibly silly of me…you’re right, this should absolutely be addressed! We added a section specifically about morning exercise. SPOILER ALERT: it’s actually EASIER to exercise while fasting! I do it as often as my schedule allows!
I have always done my morning workouts fasted (no food), regardless if a long run or a heavy weight training day as I am an “early bird.” However, I do drink a glass of water & I need my 2 cups of black coffee before I embrace my day. Does the body consider this coffee as caloric ? … and switch to glucose burning or am I safe to keep the coffee and be in a fat-burning state?
Hi Karen!
Black coffee is definitely OKAY during fasting! I drink black coffee every morning as part of my fasting routine. If someone (you or someone reading) notices a spike just from drinking black coffee, there are some people whose bodies react pretty strongly to caffeine. Gary Scheiner offers a great explanation of how caffeine can sometimes cause blood sugar spikes….but again, this does not interfere with your fasting goals: https://www.diabetesdaily.com/blog/2014/01/does-caffeine-raise-your-blood-sugar/
This was such a great read. I am a low carb eater but not keto. I exercise about an hour after waking up but eat twenty carbs first thing (taking insulin for it) with one cup of black coffee. I always ALWAYS spike heavily during my workouts, even when bolusing beforehand, running increased temp basals during the workout, and checking midway through and often bolusing again. (I know it’s the workout doing this and not my breakfast carb ratio because on the mornings I don’t workout and just eat my twenty carbs + black coffee I stay very flat on my CGM). Do you think IF would lessen the workout spike? It drives me crazy that my workout is the highest part of my day! I am fine with taking some insulin to workout but it would be nice if IF could help me blunt some of the high blood sugar I get during the workout. I appreciate any feedback you have!
Hi Meg!
I would definitely try your first IF workout with ZERO food and zero bolused insulin.
Test half-way through and again at the end and see if you still spike.
Then, if you do spike (which I suspect you will), you would simply do what I have to do if I were to weight-lift first thing in the morning on an empty stomach: take a little bit of insulin right at the start of that workout. For me, this amount was 1 unit. That 1 unit kept my BG well below 150 mg/dL during my workout. Without it, I would rise up to 250 mg/dL and beyond!
Test during your first workout with that extra bolus, too, of course. To see what happens.