Intermittent Fasting and Diabetes: What You Should Know

Intermittent Fasting and Diabetes: What You Should Know

One of the biggest food trends of recent years is intermittent fasting, and there are no signs that the fad is about to go away any time soon. Google searches show that interest just keeps growing, and mainstream media attention has been growing alongside it. The pandemic lockdowns seem to have only increased interest in the diet—perhaps spending all day at home, next to a stocked kitchen, has made this easy-to-understand diet more attractive than ever.

Intermittent fasting should be of special interest to ASweetLife readers because proponents believe that it has special benefits for people with diabetes. Do intermittent fasting and diabetes go together? Can this diet trend help you lose weight? Lower your blood sugar? Is it safe?


What is Intermittent Fasting?

Intermittent Fasting (IF) is an attractively simple diet strategy: you’re not allowed to eat anything for a certain amount of time, every day.

In essence, IF dieters choose a “window” in which they are allowed to eat, typically of 6-8 hours per day. This leads to an alternative name for the strategy: time-restricted eating. Some dieters choose even smaller windows, as little as one hour per day.

Other variations are less concerned with eating windows than with regular days of extreme caloric restriction. In the 5:2 Diet, which is extremely popular in the United Kingdom, dieters eat whatever they wish five days a week, and severely limit their intake on the other two.

Still other plans direct dieters to regularly fast for a full 24 hours. Whichever version you choose, the basic idea is the same—regular periods of extreme caloric restriction.


Where Does Intermittent Fasting Come From?

People have been skipping breakfast and practicing fasting from time immemorial, and IF proponents are eager to argue that the diet is a natural and historical way of eating, not a fad.

As a modern trend, however, IF really took off in the last decade. In the US, the most prominent advocate of intermittent fasting is probably Dr. Jason Fung, who has published several books on the subject, including one specifically for people with diabetes: The Diabetes Code. Meanwhile, a parallel intermittent fasting fad has grown in the United Kingdom since 2012—the 5:2 Diet. The 5:2 diet is less concerned with eating windows than with regular days of intense caloric restriction. Five days per week, you can eat whatever you want, but twice a week you eat very little, as little as 500 calories.

Intermittent fasting is, as of yet, not quite a mainstream treatment. Despite encouraging results in scientific studies, the American Diabetes Association has yet to officially recommend the diet, although it doesn’t exactly prohibit it either: “There isn’t enough research to support intermittent fasting as a safe long-term practice for people with diabetes. If you decide to try it, work with your health care provider to form a safe and sustainable strategy.”


What Can I Eat?

Within the eating window, dieters can apply as many additional rules as they wish. While many IF dieters choose to restrict carbs, count calories or track nutrients, the simplest interpretation allows you to eat whatever you like, and as much as you like, as long as you’re within your eating window. The simplicity of this guideline is very attractive.

It is, however, very common to advise IF dieters to choose to restrict carbohydrates; this is Dr. Jason Fung’s approach, for example. It is possible that there is an additive effect to combining low-carb and IF, especially for people with diabetes, for whom blood sugar control is of paramount importance.

Can you eat anything at all outside your feeding window? The simple answer is “no.” There is some debate over the probably small impact of a bit of cream in one’s morning coffee, for example, but the most reliable rule of thumb is to eliminate any food with caloric content.



If you use insulin to treat your diabetes, there’s one major exception to the no-snacking, no-cheating rule: carbs to prevent hypoglycemia.

It is possible that intermittent fasting can make hypoglycemia more likely to occur. If a blood sugar low were to occur during a fasting window, for whatever reason, it is incredibly important that you still consume the candy or juice that you need to raise your blood sugar back to a healthy level. The acute dangers of hypoglycemia far outweigh the very minor consequences of a broken fast.

For the same reason, you’ll need to keep an eye on your medications. The glucose-lowering effect of intermittent fasting is likely to change your pharmaceutical needs, which is why the diet should be undertaken with the permission and supervision of your doctor. You may need to adjust your dosage of insulin, as well as drugs such as sulfonylureas or meglitinides.

A couple other tips: be cautious with exercise, as fasted exercise may have unpredictable effects on your blood glucose. And be sure to stay well-hydrated.


Weight Loss

Intermittent fasting has been validated as one of the most effective weight loss strategies.

There are still arguments about over whether or not all calories are created equal, but most experts do agree: if you want to lose weight, you need to eat fewer calories than you burn. It ultimately always comes down to calorie restriction. Intermittent fasting is, at its heart, simply a new way to restrict calories.

What’s clever about IF is that it may help you restrict calories without needing to bother with nutrition trackers and food scales. Many IF dieters find that when they only eat within a defined window of 8 or fewer hours, they naturally eat less than they would otherwise, even without consciously trying to reduce calories or limit themselves.

An 8-hour window gives you time to enjoy two hearty meals—say lunch and dinner—but eliminates both breakfast and any late-night snacking.

Will you get hungry outside the window? You certainly might, but many adherents are surprised to learn how natural and easy it feels to cut out the snacking entirely.


Blood Sugar

Even if you don’t lose weight, intermittent fasting promises to provide blood sugar benefits for patients with diabetes.

Whether you have Type 1 or Type 2 diabetes, blood sugar tends to rise after meals. Fewer meals means fewer blood sugar spikes and smoother, more predictable control. This is an immediate benefit that should be easy to understand.

Over time, IF should also lead to improvements in insulin sensitivity and fasting blood glucose levels. In the healthy body, insulin levels go up around mealtime and then subside between meals, which allows the body to utilize both glucose and stored fats for energy depending on how recently he or she has eaten. The modern Western diet, with its frequent high-carb snacking, frustrates this natural metabolic cycle by perpetually flooding the bloodstream with glucose, prompting more and more insulin production and eventually the hyperinsulinemia characteristic of Type 2 diabetes. Routinely fasting gives your body a better chance of utilizing that excessive blood glucose which therefore allows insulin levels to go down to healthier levels. This, in turn, makes it easier for the body to use its stored fat as energy.

There have been many studies that have confirmed that these mechanisms deliver good results—this small one from the University of Alabama is particularly illustrative. Men with pre-diabetes were split into two groups with different time-restricted eating windows. One group had twelve hours to eat every day (from 8am to 8pm), the other merely six (from 8am to 2pm). Although the six-hour group didn’t lose weight, indicating that they ate just as much as the other group, the longer fasting period still had dramatic effects: not only did insulin levels and insulin sensitivity improve, but blood pressure improved too, and participants reported that their appetite had significantly abated. These are big metabolic benefits that can be won merely by adjusting what time of day you eat.



One of the principal benefits of IF touted by experts is the way that it engages the body’s natural process of autophagy. Autophagy is a kind of self-cleaning process that the body especially employs during fasts, scrubbing itself of dead and dying cells and actually recycling their important parts. In rodent studies, fasting-induced autophagy has shown remarkable benefits, including slowed aging and reduced risk of cancer.

The evidence for the benefits of autophagy in humans to date is somewhat less impressive than the evidence for rats, but the evidence we do have is exciting nonetheless. Neurodegenerative diseases such as Alzheimer’s, for example, seem to be related to the lack of autophagy in our daily lives, and could possibly be treated through intermittent fasting.

There’s a reason this all makes sense: most of us are probably fasting less often than we were designed to. It has been theorized that for most of our evolutionary history, we fasted with some regularity: hunting and gathering may have resulted in a natural and even perpetual cycle of feast and famine. Nowadays all but the least financially secure of us can eat whenever we wish, from morning to late evening, and most of us do exactly that, probably to our detriment.


Bottom Line

Intermittent fasting is an eating pattern that has unique potential for people with diabetes, both Types 1 and Type 2. In studies it has shown to provide both weight loss and metabolic benefits independent of weight loss, including improved insulin sensitivity. The simplicity of the diet makes it easy to follow, and many dieters report that they feel highly satisfied with the new eating pattern.

Ross Wollen
Ross Wollen

Ross Wollen is a chef and writer based in Maine's Midcoast region. Before moving East, Ross was a veteran of the Bay Area restaurant and artisanal food scenes; he has also worked as a food safety consultant. As executive chef of Belcampo Meat Co., Ross helped launch the bone broth craze. Since his diagnosis with Type 1 diabetes in 2017, he has focused on exploring the potential of naturally low-carb cooking. Follow Ross on Twitter: @RossWollen

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