Over 380 million people live with type 2 diabetes. In the US alone, over 10% of the population is diabetic, and many more are prediabetic. Without a doubt, type 2 diabetes is one of the most pervasive health crises among us today.
But there’s a shining light: Metabolic therapies like the ketogenic diet and intermittent fasting are gaining more attention. Why? Because, when done properly, they work!
In fact, there’s so much evidence on the ketogenic diet reversing type 2 diabetes that it should probably be included as one standard tool for treatment. But that will take time, since medical guidelines move about as briskly as molasses slides down a hillside.
That’s another conversation, for another day. Today, we’re exploring intermittent fasting’s applications for type 2 diabetes. This metabolic therapy follows similar principles as the ketogenic diet.
The clinical research on type 2 diabetes and intermittent fasting may be relatively limited compared to keto, but we needn't wait for any lab results to experiment with IF. Many have found it to be a safe, powerful tool in achieving body recomposition and reducing cravings for processed, sugar-loaded, or super starchy foods—all great things when fighting type 2 diabetes.
Make no mistake. This tool, if used properly, could make a serious dent in the current health crisis—and potentially a serious impact in your life, too. From the guy who has worked through his fair share of health transformations: if you’re affected by type 2 diabetes, I’d love to help inform and initiate that impact. Let’s dive in.
The Problem of Type 2 Diabetes
Type 2 diabetes is a metabolic disorder defined by high blood sugar levels, high insulin levels, high blood pressure, obesity, and insulin resistance. When someone has T2D, they're at higher risk for heart disease, cancer, Alzheimer’s, and many other chronic diseases.
How does type 2 diabetes differ from type 1? Well, type 1 diabetes is an autoimmune disease in which immune cells attack the pancreas, rendering it unable to make insulin, the hormone responsible for regulating blood sugar. Because of this, type 1 diabetics require regular shots of insulin to prevent fatal hyperglycemia.
Type 2 diabetes also involves problems with insulin, but in this case the problems are driven by diet and lifestyle factors. That’s why American diabetes rates have increased sevenfold over the past 50 years. Our genes haven’t changed dramatically, but our lifestyles have.
The cause of both diabetes and obesity is the overconsumption of food relative to one’s physiological needs and capacity to manage it. Sugar plays a big part in that. Added sugars exacerbate calorie intakes, and Americans are guzzling sugar at astronomical rates. Believe it or not, the average American adult consumes about 17% of their calories from added sugar. Sugar is addictive, and it is making us sick.
When you combine this hypercaloric American diet with a sedentary American lifestyle, you have a recipe for type 2 diabetes. To understand why, we need to cover a phenomenon called insulin resistance.
Insulin resistance describes the inability of the hormone insulin to effectively manage blood sugar levels (more precisely, it is the inability of the production of sufficient insulin to regulate energy substrate in circulation - it is energy leakage or mechanistic inefficiency). Insulin resistance is central to the pathology of type 2 diabetes, and it’s driven by the diet and lifestyle factors discussed above.
Insulin is your blood sugar levels’ boss. It’s released in response to rising blood sugar levels from the digestion of carbs, and to a lesser extent protein and fat. Yes, circulating free fatty acids raise insulin - *gasp*.
Insulin helps to sequester stored glucose and fat, and promotes the storage of blood sugar not used for energy (as either glycogen or, to a lesser degree, body fat). Because the hypercaloric modern American diet contains a lot of excess calories, and by proxy a lot of excess carbs, we store a lot of that resultant excess blood sugar via both glycogenesis and a process called de novo lipogenesis.
Imagine your excess blood sugar as luggage boarding a plane. You want that luggage stored neatly in the overhead, as glycogen. But when the overhead is full, your luggage gets tossed deep within the belly of the plane or thrown onto another flight. In our body that means it will be urinated out or stowed as body fat.
Insulin is the overworked attendant trying to help. They try to stuff your bag into the overhead, but there’s no room up there! The bag must be checked as body fat or left off the flight. That’s insulin resistance.
Insulin resistance is why supplemental insulin doesn’t reverse type 2 diabetes. It doesn’t address the underlying problem of cellular overfullness. The “overhead compartment” (our glycogen stores) remains full of sugar.
To reverse type 2 diabetes, the compartment needs to be emptied. That’s where calorie restriction via intermittent fasting comes in.
Fasting and the Metabolic Switch
During a fast, a metabolic transition occurs. Instead of relying on glucose for energy, the body begins to increase its reliance on fat and ketones—sparing glucose for the body tissues that can use only glucose.
Here’s how fasting provokes that switch:
- Fasting means not eating for a period of time, which means blood sugar and insulin levels remain low.
- Low insulin promotes the splitting of body fat (triglycerides) into fatty acids, via lipolysis.
- These fatty acids are beta-oxidized primarily in the liver to ketones.
The metabolic transition begins around 12 hours into a fast, after the liver has modestly diminished its supply of stored glucose (glycogen). With less glucose available, blood sugar falls, insulin falls, and the shift is signaled. The body begins to release stored glucose from the liver to stabilize blood glucose while also increasing the release of free fatty acids to spare that glucose.
Early weight loss for both fasting and keto is mostly water (as it is for all diets). That’s the body chewing through glycogen stores, which are mostly water weight anyway.
The History of Fasting for Diabetes
One of the earliest diabetes diets was called “starvation treatment”. Pioneered by the American doctor Fredrick Allen, this approach involved severe calorie restriction (CR) until glucose levels normalized in diabetic patients, which they often did.
Starvation treatment, however, was largely abandoned after the development of insulin therapy by Dr. Fredrick Banting in 1921 (interestingly enough, he’s a distant relative to William Banting, after whom the “Banting Diet”—itself a low-carb approach—is named). Insulin was literally a lifesaver for type 1 diabetics. But for type 2 diabetics, insulin merely offered a band-aid to cover up the underlying metabolic problems.
In the late 20th century, researchers began experimenting with a more aggressive treatment for type 2 diabetes: Bariatric surgery. When someone undergoes bariatric surgery, their stomach capacity is surgically limited.
Basically, bariatric surgery forces aggressive calorie restriction. And for that purpose, it works.
In one study, bariatric surgery succesfully normalized blood glucose in obese people with type 2 diabetes. Ten years later, 90% of the patients were still diabetes-free. It is important to note, however, that aggressive treatments also often have aggressive consequences, and nutritional sufficiency for post-bariatric patients is much more difficult to achieve.
Intermittent fasting (defined here as temporary caloric reduction for 12-36 hours) also encourages calorie restriction, but without the risk of scary surgical complications or prolonged reduction of metabolic rate. During a fast, less food comes in, allowing blood sugar and insulin levels to normalize in the diabetic patient.
Fasting may even be more effective than bariatric surgery. In a 2013 study published in Diabetes Care, simple dietary restriction led to greater weight loss and blood sugar improvements than gastric bypass in type 2 diabetics.
Intermittent fasting is also effective for weight loss, a primary target of diabetes treatment. In fact, most research on intermittent fasting has been in the context of weight loss, especially in overweight and obese populations.
Intermittent Fasting and Calorie Restriction for Type 2 Diabetes
Like we just talked about, bariatric surgery can force calorie restriction, leading to the reversal of type 2 diabetes. Now, it’s important that we differentiate between intermittent calorie restriction and the extreme calorie restriction of starvation.
Starvation results in muscle loss, trouble staying warm, incessant hunger—you get the idea. Starvation entails far less calories than the body requires.
Intermittent fasting also involves calorie restriction, but it's more about restricting when you eat than how much you eat—though a calorie deficit must be maintained for fat loss. Still, it’s nearly certain that the calorie restriction and subsequent fat loss is the component doing most of the anti-diabetes work. An example will help illustrate.
In one 2018 JAMA study, researchers split 137 type 2 diabetics into two groups: IF and CR. The IF group reduced calories by 75% twice a week, while the CR group reduced calories by 25% seven days a week. After one full year, both groups had significant reductions in HbA1c, a marker of average blood sugar.
So both intermittent and continuous calorie restriction can be effective. But let me be perfectly clear about this: it is NOT for everyone.
Who Should Exercise Caution When Intermittent Fasting?
#1: People on Blood Sugar Medications
A few notes of caution. Unsupervised fasting can lead to fasting-induced hypoglycemia, a potentially fatal situation. Those on blood sugar medications like metformin and insulin should be especially careful with fasting. The supervising doctor may want to reduce or eliminate these drugs during fasting periods.
#2: People with a History of Disordered Eating
Also, fasting should never be recommended to those with a history of eating disorders like bulimia, binge eating disorder, or anorexia nervosa. For reasons that should be obvious, intermittent fasting is not the right medicine for these conditions.
#3: People in a Period of Growth
Finally, growing children should avoid fasting. It can lead to nutrient deficiencies that may stunt growth. The same basic logic applies to folks trying to build muscle. If you want to gain lean mass, you don’t want to restrict calories.
The Future of Diabetes Treatment
Type 2 diabetes has reached epidemic proportions, but the future is bright. We’ve shown that this condition is reversible. It can be reversed or improved with the proper use of:
- The ketogenic diet
- Continuous, mild calorie restriction
- Intermittent calorie restriction via intermittent fasting
- Bariatric surgery
Both keto and IF are tools at your disposal that can repair metabolisms without surgery or starvation. Our future collective health may very well depend on these therapies. If you’re affected by type 2 diabetes, or know someone who is, I urge you: take the time to research these topics, and always consider your sources carefully. I wish you health and happiness, friends.