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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?
- A note on blood sugar levels
- Special precautions
- How intermittent fasting works
- What an intermittent fasting schedule looks like
- But won’t I be hungry?
- But isn’t eating breakfast really important?
- How to do intermittent fasting with type 1 diabetes
- Frequently asked questions
- Why I love intermittent fasting as a mom
- Final thoughts: should you try intermittent fasting?
What’s the point of intermittent fasting?
Intermittent fasting has gained attention for its potential in managing type 1 diabetes alongside traditional treatment methods. This approach may offer several benefits, supported by emerging research:
Reduced risk of hypoglycemia
Fasting could help decrease episodes of hypoglycemia in type 1 diabetes by allowing for more predictable blood sugar levels due to reduced frequency of meals.
Enhanced fat metabolism and blood sugar management
Intermittent fasting may improve fat metabolism and lower glycemic variability, contributing to more stable blood sugar levels.
Increased insulin sensitivity
There’s evidence to suggest that intermittent fasting can improve insulin sensitivity (how responsive the body’s cells are to insulin) and reduce glucose production by the liver.
Weight management
By helping with weight loss and improving body composition, intermittent fasting can play a role in managing the additional challenge of weight gain that is often associated with certain diabetes treatments.
Thoughts on the use of CGM
For people with type 1 diabetes, using a continuous glucose monitor (CGM) during intermittent fasting can provide valuable insights into blood glucose patterns, helping to identify periods of potential hypoglycemia (low blood sugar) and adjust fasting schedules accordingly.
It’s worth noting that while intermittent fasting shows promise, it’s important for people with type 1 to proceed with caution and under medical supervision. Adjustments to insulin regimens and careful monitoring of blood sugar levels are essential to avoid negative effects such as hypoglycemia.
As research continues to evolve, the use of intermittent fasting as part of a diabetes management plan should be personalized and based on feedback from healthcare providers.
A note on blood sugar levels
Before we get started: If your blood sugar drops just because you don’t eat for a handful of hours, you’re likely taking too much basal (background) insulin via pump or injection. Talk to your certified diabetes care & education specialist (CDCES) or primary care physician about “basal testing.”
(Or check out the book Think Like a Pancreas by Gary Scheiner, MS, CDCES, and do the basal testing yourself.)
Basal testing consists of purposefully skipping a meal (or two) 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.
As a general rule, if it rises, you’re not getting enough basal insulin. If it falls, you’re getting too much.
Special precautions
Before we discuss the nuts and bolts of intermittent fasting, an important note: If you have diabetes and are thinking about trying this approach, speak with your healthcare team first.
They can help you with strategies to avoid potential complications such as hypoglycemia, hyperglycemia (high blood sugar), dehydration, and diabetic ketoacidosis (DKA, a serious diabetes complication that can occur when blood sugar levels have been too high).
They can also assess if you have any conditions that increase your risk with intermittent fasting, advising whether you should avoid or postpone this approach. (The Association of Diabetes Care & Education Specialists [ADCES] has published four risk categories of fasting for people with diabetes.)
Those who have type 1 diabetes and are not in target range, for example, are considered very high risk.
How intermittent fasting works
When you wake up with an in-range blood sugar (ideally between 70 to 130 mg/dL [3.9 to 7.2 mmol/L] as a person with type 1 diabetes — 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.
This is because you have yet to introduce a new supply of glucose from food. 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, “All right! Now it’s time to burn glucose!”
Intermittent fasting takes advantage of this physiologic process by alternating periods of fasting with periods of eating.
What an intermittent fasting schedule looks like
There are a lot of different ways you can approach intermittent fasting, and after doing this myself for several years on and off, I’ve found I can flexibly create my own approach that feels most natural to me.
Types of intermittent fasting
There are a variety of different types of intermittent fasting, such as time-restricted fasting, overnight fasting, alternate-day fasting, circadian rhythm fasting, and periodic fasting.
For people with type 1 diabetes, intermittent fasting presents both opportunities and challenges. While some preliminary research suggests possible benefits, careful planning and monitoring are essential.
Here are several of the most common fasting schedules:
Time-restricted fasting (e.g., 12- or 16-hour fasting)
Eating all meals within a specific time window each day, often resulting in a daily fasting period of 12 to 16 hours.
It’s important to note that you should still eat a normal day’s worth of calories during the eating window.
If you’re trying to lose weight, that amount of calories might only be, say, 1300 to 1600, but you still need to get your allotment of calories and nutrients while following a fasting program.
24-hour fasting
Going without food for a full 24 hours, once or twice a week, from, say, dinner to dinner. This should generally only be performed once per week.
(Read this guide from John Berardi, PhD, and colleagues to see what happens if you do a 24-hour fast too often.)
Alternate-day fasting
Alternating days of regular eating with days of either complete fasting or significant calorie reduction.
Circadian rhythm fasting
Aligning fasting periods with the body’s natural circadian rhythm, such as incorporating nighttime fasting. This method involves eating the day’s meals within daylight hours and fasting during the night, which can potentially support metabolic health.
Periodic fasting
Selecting specific days for fasting each week or month.
For example, in the 5:2 method, individuals might eat normally for five days and then choose two days to significantly reduce calorie intake. This method can offer flexibility and has been explored for its potential benefits in weight management and metabolic health.
However, for people with type 1 diabetes, it’s important to approach periodic fasting with caution, considering the need for consistent carbohydrate intake to manage blood glucose levels and prevent hypoglycemia.
Moving forward
Research into intermittent fasting and type 1 diabetes is extremely limited. However, recent explorations have begun to shed light on its potential benefits for weight management and metabolic improvements in people with type 1.
Initial studies, such as a pilot study (a “small-scale test of the methods and procedures to be used on a larger scale”) published in Obesity Medicine, have shown promising results in terms of safety and effectiveness, suggesting that carefully monitored intermittent fasting may offer a viable strategy for weight loss without increasing the risk of negative events like hypoglycemia.
Similarly, a narrative review in Nutrients highlighted intermittent fasting’s potential to enhance insulin sensitivity and reduce blood sugar variability.
In early 2024, researchers at the University of Illinois Chicago started a pilot study that will eventually provide data on how time-restricted eating compares to calorie counting in people with type 1 diabetes.
However, it’s crucial to note that research in this area is still in its early stages, particularly regarding the long-term effects and best fasting protocols for people with type 1 diabetes.
Therefore, while intermittent fasting presents an interesting potential avenue for dietary management in type 1 diabetes, further clinical trials are necessary to fully understand its impact and safely integrate it into treatment plans. It’s important to consult the latest research and healthcare professionals for guidance.
But won’t I be hungry?
Guess what — it’s OK to be a little hungry. After you stop worrying about your belly not feeling full 24/7 and push through it (being sure to keep a close eye on your blood sugar levels), around 10 a.m., you might actually notice that you feel a little bit awesome. A little more clear-headed, a little more focused, maybe with 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.”
For athletes and people engaged in intense exercise, individual energy needs and responses to fasting can vary.
While some may perform well under an intermittent fasting regimen, others might find they need more consistent fueling to maintain peak performance. It’s important to listen to your body and consult with a healthcare professional to find the approach that works best 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, according to some experts.
“There haven’t been any conclusive studies that found eating breakfast to have a positive effect on weight loss or weight maintenance,” explained sports nutritionist and registered dietitian Leslie Bonci, MPH, RDN, CSSD, LDN, in Popular Science in 2017.
Also, the idea that skipping breakfast causes weight gain is oversimplified and not necessarily true. It may not be the act of skipping breakfast itself that can cause weight gain. In studies that have observed this effect, a large majority of those who skipped breakfast also lacked other healthy habits overall, which may instead have resulted in the weight gain.
“It could be that eating breakfast is simply a marker of a healthy lifestyle and, in itself, doesn’t protect against obesity,” explains a 2016 article on the website ScienceAlert.
And more recent research has continued to present mixed results on the importance of breakfast for weight management.
A 2019 systematic review and meta-analysis (analysis of data from several studies) published in The BMJ indicated that the impact of breakfast on weight and energy intake varied. This study, which looked at several randomized controlled trials, suggested that there wasn’t a clear-cut effect of eating or skipping breakfast on weight loss.
The results indicated that the general recommendation to eat breakfast might not have a universal impact on weight management. These findings highlight the complexity of dietary habits and their effects on weight, suggesting that individual dietary preferences and lifestyle choices play a significant role in weight-management strategies.
How to do intermittent fasting with type 1 diabetes
First off, be sure to get the all-clear from your doctor before you give intermittent fasting a try when living with any type of diabetes.
Using a CGM can help pinpoint when you’re at risk for hypoglycemia, making it easier to understand how your blood sugar responds to meals and fasting periods.
As you adapt to intermittent fasting, you may find a sense of mental freedom, especially if you have type 1 diabetes. This is because there’s less concern about experiencing high or low blood sugar levels after skipping breakfast.
Research indicates that intermittent fasting can influence insulin sensitivity and blood glucose stability, including in people with type 1 diabetes.
While some studies suggest that fasting can lead to more predictable blood sugar levels due to reduced meal frequency, it’s important to be aware that individual responses can vary widely.
If you stick to your fasting program consistently, you’ll likely find you lose weight and therefore increase your insulin sensitivity. This means you’ll be able to decrease your basal insulin rates, which 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, so be prepared.
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 or speak with your healthcare team for more information on determining your correction dose) and carry on with the fast, but be aware that 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 dose but is applied via pump or injection as a bolus. If this prevents morning fasting highs, it’s part of your fasting regimen. Learn more about managing the “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 (and potentially dangerous) if our overall goal is health … right? So, definitely take the insulin you need in order to be at your target 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.
- Similarly, if you develop hypoglycemia during a fast, break the fast immediately and use your hypoglycemia treatment plan to bring your levels back into target range. Remember the 15-15 rule, which recommends having 15 grams of carbs, checking your blood sugar after 15 minutes, and repeating if it’s still low. Also be sure to have a glucagon treatment on hand in the event of severe low blood glucose.
- 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 the insulin-to-carbohydrate ratios that you’re using for the food you eat before bed.
- An additional sneaky blood sugar issue to keep in mind: If this applies to you, it’s necessary 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 state.
Exercising in the morning when fasting … is actually easier (in my experience)
When you’re fasting during your exercise, it’s generally observed that aerobic or cardiovascular activities tend to lower blood glucose levels, which makes sense given the muscle’s increased use of glucose for energy.
However, certain exercises, especially those that are high-intensity like weightlifting, can trigger a rise in blood glucose. This is partly due to the body’s stress response, releasing hormones like adrenaline, which in turn prompts the liver to release more glucose.
You may therefore find that with weightlifting or other anaerobic workouts, you might actually need a bolus of insulin for that type of workout.
This will not take away from your fasted efforts — this simply helps use the glucose that’s produced when glycogen stored in your muscles is broken down during anaerobic exercise.
It’s important to find the right balance for managing blood glucose levels during different types of exercise and to consult with your healthcare team as needed for guidance.
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 p.m.).
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, or if managing fluctuating blood sugars is challenging, consider scheduling your workout for a different time;
- Check your blood sugar halfway through your workout for safety’s sake;
- If your anaerobic workout proves to typically 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, but be aware that you will be at greater risk for hypoglycemia;
- Check your blood throughout your workouts if you’re not using a CGM;
- Shower (thank you), and enjoy the rest of your fasting.
Frequently asked questions
Is intermittent fasting safe for people with type 1 diabetes?
For people with any type of diabetes, attempts to try intermittent fasting should be done only with the guidance and feedback of your physician.
In many cases, it appears to be safe. But you need to speak with your healthcare team to make sure that you don’t have any other conditions for which intermittent fasting is contraindicated and that your insulin doses and medications are properly tuned.
For people with type 2 diabetes who typically take morning medications to lower blood sugar, it’s advisable to consult with your doctor about taking the medication with the first meal of the day instead of the usual morning schedule if you’re planning to fast in the morning.
With your doctor’s OK, this adjustment can help you better manage blood sugar levels in accordance with the altered eating schedule.
For people with type 1, 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.
During your first week of fasting, check your blood sugar often during your fasting window to see how your body responds. If you stick with it long-term, you’ll likely find you will need to reduce your basal rates (even within a week or two) because intermittent fasting often has the fantastic benefit of increasing your sensitivity to insulin.
What can you drink during intermittent fasting?
During the timeframe 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.
While I lean toward minimizing artificial sweeteners and opting for natural hydration sources like water, it’s essential to recognize that health and nutrition are highly individual.
Although some concerns exist around artificial sweeteners, including their impact on health, the scientific community’s views on this are varied. It’s always best to consult healthcare professionals for advice tailored to your needs.
Read your labels carefully, and when in doubt, reach for some all-natural plain water.
Be sure to drink enough water to avoid dehydration, one of the potential risks of intermittent fasting.
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.
Although there is currently very limited research data on adding fasting to an already disciplined ketogenic diet, my personal hunch is that it would likely help with 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 during the eating period of your fasting plan.
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 (5.0 mmol/L), I know my blood sugar is still in that zone.
I don’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, and 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.
Final thoughts: should you try intermittent fasting?
If all of the above sounds appealing to you, talk to your doctor about giving it a try! (And remember that intermittent fasting won’t be appropriate or effective for everyone with type 1.)
A few things to keep in mind when embracing 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. Check out my books Emotional Eating With Diabetes or Dealing With 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 the dawn phenomenon for what is actually late-night binge eating.
- During the first few fasts, check your blood sugar more often. Even though fasting itself shouldn’t cause low blood sugars, your insulin doses simply might not be appropriate. 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 offers flexibility: Occasional deviations, like indulging in breakfast when you’re truly hungry or during special family outings, don’t derail its benefits. It’s about finding a balance that works for you, listening to your body, and not stressing over the occasional exception. It’s crucial to stay consistent with the program, but understanding that life’s unpredictability sometimes calls for adaptability. 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 to embrace fasting for a few months, then go back to a normal schedule. I’ve found that intermittent fasting has been really wonderful for me for several months at a time. Then I take a break from it for a couple of months, and eventually I naturally feel ready to follow that schedule again. Listen to your body and stay in close contact with your healthcare team to find what works for you.
- Be patient with your weight-loss journey, recognizing it as a long-term commitment rather than a quick race. If you find yourself breaking your fast prematurely to eat one of those darn office muffins, remember it’s part of the learning process. 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!
Update: I recorded this video in which I talk more about why I do fasted cardio, how I do it, and the benefits. Please let me know what you think in the comments below.
Janet
Thanks for your article. I started 16:8 IF 4 days ago. I was eating between 12-8. About 11:30 my blood sugar starts to spike. It is high for a couple of hours. I have a CGM so I can keep an eye on it. I start feeling really bad because my sugar is rising quickly. I read an article that because of my fasting my body releases cortisol and stress hormones because it isn’t getting nutrition? Help?
Christel Oerum
If your blood sugar is rising despite your fast (which is very normal) you need to either increase your basal for this time or do a small bolus correction. That doesn’t mean you’re breaking your fast, simply that you’re levelling out your hormonal response
jack berger
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
Christel Oerum
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.
Slaxx
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 🙂
Ginger Vieira
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!
Slaxx
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?
Sarah
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!
Ginger Vieira
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!
Borja
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!
Ginger Vieira
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!
Kyle
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!
Ginger Vieira
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
Shelby
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
Ginger Vieira
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.
Shelby
I see! Well I appreciate the help and response. Thank so much! That definitely cleared things up for me
Chris
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?
Ginger Vieira
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.
Antoine
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?
Ginger Vieira
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.
Emm
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?
Ginger Vieira
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!