Diabetes Self-Management Blog

I’m sure that at least a few of you have heard or read about the latest trend in weight loss called “intermittent fasting.” The very word “fasting” is probably less than appealing, as it pretty much means you don’t eat or drink anything (except perhaps water) for a specified amount of time. Starvation is not exactly recommended among health professionals. But intermittent fasting is different. Is it something you should try?

What is intermittent fasting, anyway?
Intermittent fasting has been the talk of the town, so to speak, thanks to two recent books to hit the market: The Fast Diet by Dr. Michael Mosley and Mimi Spencer, and The Overnight Diet by Caroline Apovian, MD. Intermittent fasting essentially means that you skip a meal or severely restrict calories on certain days of the week with the intention of losing weight, controlling blood glucose, and/or decreasing heart disease risk. But on the other days of the week, you can pretty much eat what you want (within reason, of course). For many people, this concept sounds appealing. Limiting calories for a couple days a week doesn’t sound that bad if you can eat what you want the rest of the time.

The Fast Diet, also called the The 5:2 Diet has you eat between 500 and 600 calories (women get 500 calories, men get 600 calories) for two days out of the week, spread over two meals of about 250 to 300 calories. These fast days should not be right in a row, and your food choices ideally should be more plant-based and emphasize protein. The premise is that after several hours of fasting, the body burns up its carbohydrate stores and shifts to burning fat for fuel. Many claim that intermittent fasting also helps to blunt appetite.

The Overnight Diet emphasizes getting enough sleep; a lack of sleep can disrupt metabolism, making it hard to lose weight. Sufficient sleep, according to the author, will reduce hunger pangs. The diet part of this involves drinking homemade smoothies once a week, and eating a low-calorie, high-protein diet the remaining six days of the week.

Does intermittent fasting work?
In many ways, these two diets sound like just another fad to come around the bend. And maybe they are. However, there actually is some credible science behind fasting. Restricting calories in the diets of animals appears to increase their lifespan, for example. Recently, a team of researchers in the UK looked at the various approaches to intermittent fasting, with a focus on how they might help (or hinder) those with Type 2 diabetes and obesity. They found that intermittent fasting is as effective as or even more effective than simply cutting calories to lose weight.

They also found that intermittent fasting has other health benefits, including reducing inflammation, lowering blood pressure, lowering heart rate, lowering cholesterol, and reducing insulin resistance. This unique approach may even help prevent the development of Type 2 diabetes. Followers of the diet also believe that intermittent fasting can prolong your life and prevent Alzheimer disease.

Is intermittent fasting for you?
Sound appealing? Before you jump on the intermittent fasting bandwagon, realize that not a whole lot of research has been done in this area, at least with humans. The few studies thus far look promising: In one study, fasting was shown to lower blood pressure and cholesterol, and on “regular eating” days, the subjects did not overindulge, which has been a concern. But again, we still don’t know a whole lot about intermittent fasting.

Wondering what you might eat? A sample 500-calorie menu from The Fasting Diet is steel-cut oatmeal with ½ cup blueberries for breakfast, and then chicken stir-fry made with 5 ounces of chicken and some vegetables, along with a tangerine for dinner. That’s it. Would that hold you?

Could intermittent fasting be harmful? Well, that depends. If you take insulin or sulfonylurea drugs to control your blood glucose, intermittent fasting can considerably raise the risk of low blood glucose unless you make appropriate adjustments. This way of eating is not suitable for pregnant women, people under the age of 20, people who are underweight, and people who have an eating disorder. It may also not be good for people who take certain types of medicines, such as beta-blockers.

Another question to ask yourself: Can you stick with this way of eating? It may sound simple to just eat 500 calories for two days a week, but 500 calories isn’t all that much. On those days, you’re likely to feel tired, grumpy, anxious, and irritable. You also may not sleep well and your breath might not exactly smell like a bed of roses.

But, if you’d like to give intermittent fasting a try, talk it over first with your health-care provider and decide together if it’s something that could work for you. And if you have tried this, feel free to share your experience!


  1. I’d be a little worried about hypoglycemia if I took a thiazolidinedione (pioglitazone, rosiglitazone) or bromocriptine. But certainly the risk is much greater with insulin and sulfonyureas, as you say.


    Posted by Steve Parker, M.D. |
  2. Amy: none of this makes much sense to me. I need to keep my liver out of the mess and the way I do that is timely and regular eating of sufficient calories,

    This article makes no sense for me. Best wishes and special thanks for all the excellent articles and eating issues.

    Posted by jim snell |
  3. I was wondering if anyone knows if eating more than the 500-600 calories would still work. I think I would be violent if I only ate that little, but because I’m in the process of losing weight gradually, eating 1,000 calories on those “fasting” days would still be less without being so low that I feel cranky. Any thoughts?

    Thanks for the info/ideas.

    Posted by Sue Dean |
  4. I remember doing a three day ‘fast’ over 50 years ago… partially because I ran out of money and food. The first day was not very nice, but I noticed by the second day my body (and mind) decided we must be starting a famine period. As long as I drank water it wasn’t really a problem. I did appreciate food when I resumed my normal eating pattern though.

    It hasn’t been that long that we have had access to food all of the time. Perhaps our bodies are programmed to do without. Certainly in some places that still is the norm. And perhaps some of us end up as type 2 diabetics because we have ‘thrifty genes’… which of course would ensure over survival in the times of very little. The lean didn’t make it while the plump type 2s had reserves.

    There have been studies to show that when the body isn’t always busy processing food, it turns to healing modes it doesn’t always get a chance to do.

    Of course if you are on any diabetic meds (or type 1) you might want to think twice before you try it out.

    Posted by JohnC |
  5. I quit reading books. No one agrees and they all have different solutions. I would never do intermittent fasting when the program I follow now works.

    Posted by Ferne |
  6. I have type 2 on metaforming 2xday 500ea for 4 hrs My a1c was 7.1 for few years and went to 7.3 My morning blood sugars were creeping up some times up to 18 after a meal I keep low carbs limited no pasta potatoes take only stevia .my last visit to the dr he increased my metaformin to 1500 mg 5003x per day
    Instead I read dr mercola intermittent fasting and give it a try I try to stop ,around 6-7 pm and eat my regular breakfast at 11-12 A month after my sugars in the morning6.8 to 7.6 and after every meal went from 14-18 to 9.9 -7.6
    I don’t agree with the food piramyd I prob be on insulin if I ate like the diabetic clinic recomended (I live in Canada) instead I followed a naturopath more healthy diet
    So far this is working out and definitely lower my sugars I just got my blood test and dr didn’t call me
    So I will find out and post later if my a1c went down
    I am less hungry and crave sweets a lot less

    Posted by Pat |
  7. I have had Type 1 diabetes for 28 years, and I wear a continuous glucose monitor (CGM) and insulin pump.

    I’ve noticed that when I eat a higher fat diet, or when I don’t exercise, my body does not react to insulin well, similar to what happens in Type 2 diabetics.

    I tried intermittent fasting and what I noticed is that in the days after fasting, my metabolism is supercharged. My body’s uptake of insulin is significantly more efficient, even when eating fatty foods. Foods that should have sent my blood sugars lingering for hours into the 200+ range barely budge me. (Remember, I have the CGM which plots out my blood sugars every five minutes, 24 hours a day. So I have hard data to back up my observations.)

    If you’re type 1, you have to be very careful about hypoglycemia. But I’m now able to “ride” my insulin pump basal levels to counter the effect of fasting so that I do not dip into hypoglycemia.

    This has been a real eye-opening experiment for me.

    Posted by Adam |

Post a Comment

Note: All comments are moderated and there may be a delay in the publication of your comment. Please be on-topic and appropriate. Do not disclose personal information. Be respectful of other posters. Only post information that is correct and true to your knowledge. When referencing information that is not based on personal experience, please provide links to your sources. All commenters are considered to be nonmedical professionals unless explicitly stated otherwise. Promotion of your own or someone else's business or competing site is not allowed: Sharing links to sites that are relevant to the topic at hand is permitted, but advertising is not. Once submitted, comments cannot be modified or deleted by their authors. Comments that don't follow the guidelines above may be deleted without warning. Such actions are at the sole discretion of DiabetesSelfManagement.com. Comments are moderated Monday through Friday by the editors of DiabetesSelfManagement.com. The moderators are employees of Madavor Media, LLC., and do not report any conflicts of interest. A privacy policy setting forth our policies regarding the collection, use, and disclosure of certain information relating to you and your use of this Web site can be found here. For more information, please read our Terms and Conditions.

Nutrition & Meal Planning
Hype or Healthy? Ezekiel Bread and Whey Protein (10/20/14)
Hype or Healthy? Chia Pudding and Bulletproof Coffee (10/14/14)
Low-Carb Diet Improves Quality of Life in Type 2 Diabetes (10/07/14)
Soup Really Is Good Food (10/06/14)



Disclaimer of Medical Advice: You understand that the blog posts and comments to such blog posts (whether posted by us, our agents or bloggers, or by users) do not constitute medical advice or recommendation of any kind, and you should not rely on any information contained in such posts or comments to replace consultations with your qualified health care professionals to meet your individual needs. The opinions and other information contained in the blog posts and comments do not reflect the opinions or positions of the Site Proprietor.

Blood Glucose Self-Monitoring — Part 3: Smart Monitoring

10 Keys to Long-Term Weight Loss

Take Your Best Shot: Stay Up to Date on Vaccines

Complete table of contents
Subscription questions