Intermittent Fasting: Is it Healthy? Does it Work? Is it Dangerous?

By Dr. Jeremy Webster

Obesity is a big problem today. The CDC estimates the adult obesity rate in the United States to be around 35%, and that number is growing at a shocking rate.  If we don’t make changes soon, that number could exceed 50% early next decade! With obesity comes many health problems, such as diabetes, heart disease, joint pain and inflammation, cancer, and other chronic diseases. Obesity is not just a cosmetic problem; it’s a serious health problem.

With problems come solutions, often many solutions. Some of which work and others that might not work. Over the years, the “experts” have offered many diets that promise a quick fix to the obesity dilemma. Low-calorie, low-fat, low-carbohydrate, paleo, vegan, carnivore, and Mediterranean diets have all claimed to be the secret to a healthier, leaner, and hopefully better life. But many of these plans have failed to produce long-lasting and consistent results.  

Between about 2012 and 2016, a series of books by Dr. Michael Mosley, Kate Harrison, Dr. Jason Fung, and others started to popularize another type of diet that seemed to be backed by a lot of promising science. That diet became known as Intermittent Fasting (IF). The miracle we had all been looking for, or so it seemed.

The initial problem with intermittent fasting was defining it.  Some advocate a very low-calorie diet for two days per week followed by five days of regular eating. Others suggest 3-5 days of very low-calorie consumption per month, while others suggest skipping meals from time to time. The common theme being that you plan intervals where you avoid or restrict food consumption followed by times of normal food consumption.   

Commonly reported benefits of all types of IF seem to include weight loss, improved insulin sensitivity, and better blood sugar control, along with a newly introduced term to the common lexicon: autophagy. It seems that nutritionists, trainers, doctors, and other experts can no longer discuss diet at any length without throwing out the term “autophagy” to strengthen their stances on diet. “Keto stimulates autophagy.” “Autophagy is enhanced by Time-Restricted Feeding.” “Intermittent fasting is a great way to boost autophagy.” But what is autophagy? And is it really something we should seek in a diet?

Autophagy is a process we use to clear excess proteins from our bodies. Every day we build new proteins to form bones, muscles, joints, organs and other tissues. Sometimes we produce a bit too much protein in certain parts of the body and the excess protein needs to be cleared, otherwise it will build and form a plaque. Plaques seen in cataracts, blood vessels and the brains of Alzheimer’s patients all respond positively to diets that promote autophagy. A 2018 review of cancer research by Antunes found that diets promoting autophagy tend to enhance cancer treatments and reduce the negative side effects of such treatments. While more research into autophagy-promoting diets and cancer is needed, the initial studies are promising. Overall, diets that promote autophagy, such as IF, seem to be of value for weight management and the promotion of health. 

What type of IF is best?

Two important factors play into assessing the worth of a diet: Is a diet sustainable? And does the diet help you achieve your goal?  Both are necessary. A diet that produces fantastic results but is very difficult to perform is not a good diet because most people will not stick with it. A diet that is easy to perform but gives poor results, well that one is obviously not desirable. With these two factors in mind, the type of intermittent fasting most promoted by “experts” and most performed by diet-goers is a type known as Time Restricted Feeding (TRF). TRF is generally considered easy to perform and the latest research suggests it just might work, but only if performed correctly! 

Time Restricted Feeding is a form of IF that takes place over a 24-hour period. It requires a set block of time each day designated for feeding and a block of time designated for fasting. An example would be 14:10 TRF, where you fast for 14 consecutive hours, followed by 10 consecutive hours where you consume your food for the day.  Breakfast at 8 a.m., lunch at 12:30 p.m., and an early dinner finished at 6 p.m. would qualify as 14:10 TRF.  A mid-morning or mid-afternoon snack would be allowed, provided no calories from food or drink are consumed during the 14-hour fasting window from 6 p.m. to 8 a.m.   This type of early TRF (eTRF) is healthy and happens to be the exact type followed by renowned fasting researcher Satchin Panda.  But this is not the most performed version of TRF. 

Today, the masses are performing a form of fasting called 16:8 TRF with a feeding window from noon until 8 p.m. Essentially, these fasters simply skip breakfast. This form was born from a desire for convenience and a fundamental misunderstanding of the research on fasting.  While there is nothing wrong with 16:8 TRF in its simplest form, the timing as performed by most (skipping breakfast) is in fact, dangerous.  

A 2015 study published in the Journal of Physiology and Behavior found that breakfast skippers had higher blood pressure and higher levels of stress hormones. They concluded that this might result in heart disease.  A 2019 study in the Journal of the American College of Cardiology confirmed this hunch and concluded: “skipping breakfast was associated with a significantly increased risk of mortality from cardiovascular disease.” Further studies suggest that breakfast skipping may worsen sugar metabolism and insulin resistance, which is why short-term weight loss does not seem to benefit from breakfast skipping versus other types of calorie restriction. Long-term weight loss is often hindered by skipping breakfast due to excess stress hormones.  

With all of this in mind, it is important to get it right if you want to reap the benefits of intermittent fasting. These steps will keep it simple:

Avoid the potential dangers by always starting your day with a good breakfast within 1-2 hours of waking. Be sure to include high-quality protein, healthy fats, and fiber-rich whole fruits or vegetables with breakfast.    

Continue to eat healthy whole foods throughout the day, and avoid highly processed foods. This will boost health by improving blood sugar and enhancing autophagy (cleansing of plaques) even if you do not partake in intermittent fasting. 

Consume dinner as early as possible and avoid food or calorie-containing drinks after you have finished dinner.  Try to limit your “feeding window” to 12 hours or less (eight to 10 hours is even better). Continue to hydrate with fresh water as you wind down the evening.

By following these steps, you will avoid any possible dangers of getting intermittent fasting wrong. You will likely notice a daily calorie reduction and weight loss along with improvements in digestion, better sleep, and an overall boost in energy and vitality.