Over the years I’ve tried many ways to shape up, lose weight and control Type 1 diabetes (T1D) blood sugar with varying success.  Three years ago, I read a few articles about Intermittent Fasting (IF). I was curious, but dubious.  It seemed fad-ish, difficult, and unlikely to work for me.

[here’s where you expect me to say “I tried it and it changed my life.  I lost 80lbs, won a MacArthur Genius Award and was featured as The Economist Magazine’s World’s Sexiest Man…and you can too if you just send 1 cent plus $99.99 for postage and handling to Coach David’s overseas bank #8675309”] but that’s not happening.  I’ll merely give you brief summary of the what, how, why IF may be worth looking into.

Thing #1: IF may not be not safe, healthy or right for everyone. If it intrigues you as a way to manage weight or address chronic conditions like irritable bowel syndrome, high cholesterol or arthritis you should ask your physician first. Researchers say avoid IF you are:

  •   a child/teen under age 18
  •   pregnant or breastfeeding
  •   a diabetic with blood sugar problems (I coordinated with my endocrinologist, IF improved my blood sugar control)
  •   someone with a history of eating disorders

That said, IF can be a safe element of a lifelong strategy to promote wellness, BUT a change like this affects different people in different ways so even after consulting with your doctor, be alert and cease IF if you experience unusual anxiety, headaches, nausea or other symptoms.

Like full contact karate or naked skydiving, IF may not be right for everyone.

Many people automatically opt to change what they eat when trying to lose weight or improve blood sugars.  IF shifts the approach to changing when you eat.  With IF you only eat during specific times while fasting for a period of time OR you may eat at a specific time OR eat just one meal a couple days a week.  This approach may help your body burn fat and may also provide other health benefits.

Mark Mattson, a neuroscientist at Johns Hopkins University (JHU) who has studied IF for 25 years explains the rationale behind IF by noting that our bodies evolved to be able to go without food for many hours or even several days or longer because our prehistoric ancestors were hunters and gatherers who did not know how to farm so they needed to be able to survive for long periods when they couldn’t gather or hunt.

JHU dietitian Christie Williams, M.S., R.D.N., explains that even 50 years ago, it was easier to maintain a healthy weight because “there were no computers, and TV shows turned off at 11 p.m.; people stopped eating because they went to bed. Portions were much smaller. More people worked and played outside and, in general, got more exercise.” Nowadays, TV, Internet and other media are available 24/7 so we stay up viewing favorite shows, gaming and chatting online. We sit, snack, remain sedentary at computers all day—and deep into the night, and we get less sleep. Today’s extra calories paired with inactivity and less sleep create a higher risk of obesity, more type 2 diabetes, heart disease and other illnesses. Scientific studies show that IF may help reverse these trends.

WHAT is IF? As noted by JHU researchers (see link below), options to consider after checking with your doctor and get their “go-ahead” include:

  •       a daily approach where you restrict daily eating to one 6-to 8-hour period, e.g., maybe try 16/8 fasting in which you eat during 8 hours/fast for 16 (people find this pattern easier over the long term since many of the hours happen while you sleep!)
  •       Another option is the 5:2 approach. You eat regularly five days a week and limit yourself to one 500–600 calorie meal two days, say Monday and Thursdays
  •       NOTE: Longer periods without food, such as 24, 36, 48 and 72-hour fasting periods, are not necessarily better for you and may be dangerous because going too long without eating might encourage your body to start storing more fat in response to starvation
  •       NOTE 2: JHU’s Mattson’s work shows that it can take 2-4 weeks before the body becomes accustomed to IF. You might feel hungry or cranky while you acclimate to the new routine, but he’s observed that research subjects who make it through the adjustment period tend to stick with the plan, because they notice they feel better.


  •       During the times when you’re not eating, water and zero-calorie beverages such as black coffee and tea are permitted
  •       During your eating periods, “eating normally” does not mean going crazy since you won’t lose weight or get healthier if you pack your feeding times with high-calorie junk food, super-sized fried items and treats
  •       When eat, enjoy a range of foods as JHU Dietician Williams says, “We want people to be mindful and take pleasure in eating good, nutritious food,” and share the mealtime experience with others since this adds satisfaction and supports good health
  •       Williams, like most nutrition experts, regards the Mediterranean diet as a good blueprint of what to eat, whether or not you try IF, “you can hardly go wrong when you pick complex, unrefined carbohydrates such as whole grains, leafy greens, healthy fats and lean protein.”


  •       Research shows that IF periods do more than burn fat. Per JHU researcher Mattson “When changes occur with this metabolic switch, it affects the body and brain.” One of Mattson’s studies published in the New England Journal of Medicine revealed data about a range of health benefits associated with IF including a longer life, a leaner body and a sharper mind. “Many things happen during intermittent fasting that can protect organs against chronic diseases like type 2 diabetes, heart disease, age-related neurodegenerative disorders, even inflammatory bowel disease and many cancers”
  •       Research has revealed these potential benefits of IF: Boosts in thinking and memory in animals and verbal memory in adult humans; Heart health benefits like improved blood pressure, lower resting heart rates and more; Physical performance improved in a study on young men who lost fat while maintaining muscle mass when doing 16-hour fasts; Mice that were fed on alternate days had better running endurance; in animal studies on diabetes and obesity, IF prevented obesity. In six brief studies, obese adult humans lost weight through IF; Tissue health in animals showed that IF reduced tissue damage during surgery and led to improved results

Per a Mayo Clinic Healthy Lifestyle posting cited below, Dr. Manpreet Mundi said that some studies suggest that alternate-day fasting is about as effective as a typical low-calorie diet for weight loss because reducing the number of calories you eat helps you lose weight, and a Harvard Journal study (cited below) says that “there’s a ton of incredibly promising IF research done on fat rats that lose weight, improve their blood pressure, cholesterol, and blood sugars… but they’re rats. Studies in humans, almost across the board, have shown that IF is safe and effective, but really no more effective than any other diet. In addition, many people find it difficult to fast” So it ain’t a miracle, just a potentially productive alternative to consider and there is a growing body of research that suggests that the timing of the fast is key, and can make IF a more realistic, sustainable, and effective approach for weight loss, as well as for diabetes prevention.”

How IF supports weight loss, noted in the Harvard Journal article cited below

The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains (think white flours and rice), are quickly broken down into sugar, which our cells use for energy. If our cells don’t use it all, we store it in our fat cells as fat. But sugar can only enter our cells with insulin, a hormone made in the pancreas. Insulin brings sugar into the fat cells and keeps it there.  Between meals, as long as we don’t snack, our insulin levels will go down and our fat cells can then release their stored sugar, to be used as energy. We lose weight if we let our insulin levels go down. The entire idea of IF is to allow the insulin levels to go down far enough and for long enough that we burn off our fat.

IF and reduced inflammation

Per some research, IF may be more beneficial than other diets for reducing inflammation and improving conditions associated with inflammation, such as:

  • Alzheimer’s disease
  • Arthritis
  • Asthma
  • Multiple sclerosis
  • Stroke

Unpleasant side effects IF (that usually go away within a month)

  • Hunger
  • Fatigue
  • Insomnia
  • Nausea
  • Headaches

Why might changing the time you eat help?

An in-depth review of the science of IF recently published in New England Journal of Medicine sheds some light. Evolution embedded fasting within our physiology, triggering several essential cellular functions. Flipping the switch from a fed to fasting state does more than help us burn calories and lose weight. The researchers combed through dozens of animal and human studies to explain how simple fasting improves metabolism, lowers blood sugar levels; and reduces inflammation, which improves a range of health issues from arthritic pain to asthma; and even helps clear out toxins and damaged cells, which lowers risk for cancer and enhances brain function.

Is intermittent fasting as good as it sounds?

According to metabolic expert Dr. Deborah Wexler, Director of the Massachusetts General Hospital Diabetes Center and associate professor at Harvard Medical School, says “there is evidence to suggest that the circadian rhythm fasting approach, where meals are restricted to an eight to 10-hour period of the daytime, is effective.” But still, she recommends that people “use an eating approach that works for them and is sustainable to them.”

There is some good scientific evidence suggesting that circadian rhythm fasting, when combined with a healthy diet and lifestyle, can be a particularly effective approach to weight loss, especially for people at risk for diabetes. You should follow up if you think IF might be good for your road to well-being.

Good overall review from Hopkins Medicine


Mayo Clinic Healthy Lifestyle post also offers a good brief summary


Harvard Journal study, has some good citations if you want more info


Sample explainers available on YouTube