Intermittent Fasting: Good or Bad?

Is the “fast and feast” style of eating a healthy way to shed unwanted pounds or just another fad?


Photo by: rez-art


This “fast and feast” style of eating is the new way of dieting. One day you “fast” by limiting food to 500 calories, while the next you “feast” by eating as you normally would. But is this flip-flop lifestyle a healthy way to shed unwanted pounds, or just another fad?
The Intermittent Fasting Trend

Several books about intermittent fasting have recently been released. The Every Other Day Diet: The Diet That Lets You Eat All You Want (Half the Time) and Keep the Weight Off was written by Dr. Krista Varda, an assistant professor of kinesiology and nutrition at the University of Illinois, who began studying the effects of intermittent fasting on mice. Based on her post-doctoral research conducted at the University of California Berkeley, she found that mice ate only 25 percent more on feast days and didn’t compensate for the lack of food provided on fast days.

A second popular book titled The Fast Diet, written by Dr. Michael Mosley and Mimi Spencer, uses the same concept, except you can choose which two non-consecutive days each week to fast. This method of intermittent fasting is also known as the 5:2 approach (five days feasting, two days fasting).


If you choose to intermittently fast, you’ll probably lose weight. Studies have found that on days after fasting, folks don’t tend to overindulge to make up for the calories lost from the fasting days. A December 2014 study published in Cell Metabolism found that mice fed according to this dietary pattern had a number of therapeutic health benefits for diseases such as obesity and type 2 diabetes. However, this study was conducted only in mice, and it's tough to determine if humans would react the same way.

A 2011 study published in the International Journal of Obesity had 107 overweight or obese premenopausal women follow an intermittent-fasting-type plan. Compared with ladies who followed a continuous-calorie-restricted plan, their weight loss was about the same. In addition, after six months, those who intermittently fasted had lost an average of 14 pounds each.

This type of plan promotes a diet high in fiber, especially fruits and vegetables. Eating a diet high in fruits and vegetables is commonly recommended for folks looking to achieve heart health and also to help lower blood pressure.

Keeping hydrated, especially with low-calorie beverages like water and herbal tea, is promoted on this plan. So is exercise, though you’re supposed to continue your regular exercise regimen even on fast days.

Another advantage of intermittent fasting is the simplicity of the rules, which makes it easier to follow. As long as you can count calories and restrain your hunger, you’re good to go.


The Fast Diet (a type of intermittent fasting) rated 28 out of 31 in U.S. News & World Report's rankings for best overall diet. Intermittent fasting is downright dangerous for women who are pregnant or planning on becoming pregnant, children, or people with type 1 diabetes. It’s also not appropriate for anyone with an eating disorder. If you have a medical condition or are taking medications, it is important to speak with your medical doctor before choosing this dieting style.

When compared with the USDA’s Dietary Guidelines this plan falls short on numerous good-for-you nutrients including fiber, potassium, calcium, and vitamin D. This is not very surprising, since on two or more days during the week (depending on the type of intermittent fasting you choose to follow), you won’t be taking in enough food to supply all the nutrients your body needs.

Hunger and lethargy are to be expected on days you fast. Trying to work and concentrate while you’re very hungry is virtually impossible.

Studies have found that one of the best ways to lose weight is by changing lifelong habits. Intermittent fasting doesn’t address healthy habits or direct you in how to make lifelong healthy changes. Although a handful of studies have been done on intermittent fasting, there are still a lot of unexplored questions.

The Bottom Line: Intermittent fasting is another trend that has taken the dieting world by storm. But until further research is conducted, following this plan isn’t recommended.

Toby Amidor, MS, RD, CDN, is a registered dietitian and consultant who specializes in food safety and culinary nutrition. She is the author of The Greek Yogurt Kitchen: More Than 130 Delicious, Healthy Recipes for Every Meal of the Day.

Keep Reading

Next Up

The Latest on Intermittent Fasting

A nutritionist looks at the latest newest research on intermittent fasting.

What's the Deal with Intermittent Fasting?

Here's what you need to know before you jump into IF.

Pasta: Good or Bad?

Trying to find healthy and delicious recipes? Food Network makes that easy with their collection of low fat, low calorie and low carb recipes.

Eggs: Good or Bad?

Over the years, eggs have gotten a bad rap as cholesterol no-nos. But should you totally ditch them in your diet?

Caffeine: Good or Bad?

Can’t go without that morning latte or afternoon soda, but worried you're overloading on caffeine? Here are some tips to help you assess your daily dose of caffeine.

Pork: Good or Bad?

There has been controversy lately about whether pork is healthy or safe to eat. So you can make your own educated decision, we offer the nutrition facts on pork. Is it really the “other white meat”?

Cream: Good or Bad?

With boatloads of calories and artery clogging saturated fat, can cream be part of a healthy diet?

Coffee: Good or Bad?

Americans consume 400 million cups of coffee per day. In Italy, people down 14 billion espressos every year. But the coffee-guzzling king is Finland, where residents drink more coffee than anywhere else in the world. Clearly, coffee is one of our favorite beverages, but is it good or bad?

Milk: Good or Bad?

We're talking about cows' milk, that is. Many folks view milk as wholesome and healthy. Others, meanwhile, warn us away and say it's full of hormones or might make you phlegmy. So what’s the deal with milk: does it do your body good or not?

Mayo: Good or Bad?

It’s the quintessential “bad” food laden with artery clogging saturated fat. For years, we’ve been told to “hold the mayo,” but is it really as bad as they say?