Intermittent Fasting May Not Be So Great, New Research Suggests

If weight loss is the goal, you may want to consider a different diet.

September 29, 2020
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Photo by: lacaosa/Getty Images

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Intermittent Fasting (IF) has quickly become one of the hottest fad diets around, but is this time restrictive method of eating safe and effective? A new study suggests there may be some undesirable consequences.

If you dive into the research, you’ll find studies exploring IF for all kinds of ailments including diabetes, cancer and cardiovascular disease. At the end of the day there’s not a whole lot of evidence touting the beneficial effect of IF for weight loss and practically none of the research has been done in humans, only laboratory animals. A review study published in 2014 compared human and animal data and determined the effects in each of these subject pools varied.

A study published this week explored the effect of time-restricted feeding (TRF), one of the most popular methods of IF, to good-old-fashioned three-meals-a-day on a group of overweight and obese men and women. More than 100 subjects ages 18 to 64 were divided into two randomized groups. The consistent meal timing (CMT) group ate three meals a day, while the TRF group could eat without restriction only between the hours of 12 p.m. and 8 p.m. Subjects were not given a diet to adhere to and were instructed not to change their physical activity.

After the 12-week study, researchers found that both groups lost modest amounts of weight, about two to three pounds total. While the TRF group lost slightly more weight, much of it was muscle as opposed to the more desirable fat loss. Researchers speculated that the fasting group may not have been consuming enough protein. The shortened window of protein intake may also be to blame as the body's demand for protein lasts throughout the day.

Bottom Line: We’ve got a lot more research to do before we truly understand the benefits of IF for weight loss but if you do try IF, aim to get adequate amounts of daily protein.

Dana Angelo White, MS, RD, ATC, is a registered dietitian, certified athletic trainer and owner of Dana White Nutrition, Inc., which specializes in culinary and sports nutrition. She is the author of four cookbooks First Bites: Superfoods for Babies and Toddlers, The Healthy Air Fryer Cookbook, The Healthy Instant Pot Cookbook and Healthy Quick and Easy Smoothies.

*This article was written and/or reviewed by an independent registered dietitian nutritionist.

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