Intermittent Fasting: Is timing the key to health?


For most people, dieting usually involves changing what goes on your plate – and often the portion size. But what about the timing?

Recently, there has been increased attention devoted to eating patterns through intermittent fasting as a means to lose weight and promote wellness. But does this work? Is it even safe?

What is Intermittent Fasting?

Intermittent Fasting (IF) is a strategy where individuals restrict eating for a set amount of time. There are different IF schedules being popularized, but the more common regimens involve only eating during specific 3, 8, or 12-hour windows or fasting for 24 hours at a time. IF does not necessarily mean less calories – there are often no restrictions for what or how much you eat, the focus is on when you eat.

What do the studies say?

Several studies have researched various IF regimens in animals — primarily mice and rats — and have shown positive health effects including weight loss, improved cholesterol levels, and enhanced insulin sensitivity. It is unclear if these benefits can be attributed exclusively to IF or if they are a result of the weight loss seen with IF. In other words, it is possible that the same health benefits can be seen with other methods that produce weight loss.

Though these studies provide exciting results, they cannot be directly applied to humans. The human trials that have been conducted are limited and inconsistent, so more research is needed.

Intermittent Fasting has gained traction in the athletic community because of claims of muscle gain and decreased fat mass. However, no scientific studies have looked at IF and the effect on muscle gain. Alternatively, studies have shown that exercise in a fasted state increases muscle protein breakdown. In fact, it is often recommended to have a pre-workout snack to promote muscle protein synthesis.

Is it for you?

Like any diet plan or program, no matter what benefits are reported, it is only effective if it can be applied and sustained. This may be very difficult with IF because of the frequent food restrictions and the characteristic feelings of hunger. It may be especially challenging to have a schedule that includes daily periods of fasting as we encounter weekend gatherings and tempting seasonal fare.

Fortunately, there are other lifestyle habits that may be more easily adopted and have already been shown to provide health benefits similar to the ones seen in animal IF studies. These habits include eating a well-balanced diet, eating more fruits and vegetables, and getting 30 minutes of physical activity 5 days a week.

About the author:

Anna Nakayama is a dietetic intern at MGH, completing her year-long comprehensive training in nutrition. She completed her Bachelor’s degree in Nutrition at Cal Poly, San Luis Obispo in 2013 and double concentrated in Applied Nutrition and Culinary Science & Management. Anna loves to travel and experience different cultures and cuisines. She is looking forward to her upcoming trip to Malawi to work on a clinical trial for a nutritional supplement.

Our Be Fit Nutritionists are comprised of dietetic interns studying at Massachusetts General Hospital. During their internship, they receive training on acute care nutrition, ambulatory and community nutrition, food service systems management, and research. Their comprehensive work is done in collaboration with registered dietitians.

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