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Downside of Intermittent Fasting

Intermittent fasting is a very popular weight lost strategy. However, a new study found that one form of fasting, called time-restricted eating, delivered little weight loss but muscle loss, a downside of intermittent fasting.  

Downside of Intermittent Fasting
Time-restricted eating may be a downside of intermittent fasting.
Photo by health.harvard.edu

This new study, published in JAMA Internal Medicine, is one of the most in depth studies to analyze time-restricted eating, that includes fasting for 12 or more hours each day. Many followers of the diet routinely skip breakfast and eat all his or her meals between noon and 8 p.m., ending in a daily 16-hour fast.

Intermittent Fasting Boosts Weight Loss

Past studies have shown that fasting jumpstarts weight loss and improves metabolic health. However, much of the data has come from animal studies or small experiments of very short duration in humans. Experts say the diet is successful because it allows people to eat what they want in a given timeframe.

Downside of Intermittent Fasting

The study found that overweight adults who fasted for 16 hours daily, gained little to no benefit. Over the course of the three-month study, they lost an average of just two to three and a half pounds. The weight loss was slightly more than the control group. The majority of the weight the participants lost was not body fat but “lean mass,” which includes muscle.

Eat More Protein!

Although it is normal to lose some muscle during weight loss, the fasting group lost more than expected. Muscle mass has many health benefits including increasing metabolism and helping people to prevent weight from coming back. One reason for the muscle loss may have been that the fasting diet made people eat less protein, says researchers.

Some experts warned that the study was too short for a weight loss trial. Researchers said the fasting group would have showed more weight loss if the research had been longer with more participants. Experts said previous research has shown people do better when they eat most of their calories early in the day. This is when our bodies are better able to metabolize food, rather than skipping breakfast and eating later.

 Other studies have found that individuals can maintain muscle while fasting by doing resistance training and consuming more protein. Dr. Weiss, who is a cardiologist at the University of California, San Francisco, said the findings need to be analyzed further. For now he remains skeptical of time-restricted eating.

“This was a short study, but it was enough of a study that to me it calls into question whether this works. If it does work, then the magnitude of the benefit is very small,” Dr. Weiss said.

The Bottom Line

The good news is that intermittent fasting will still help you lose weight. However, muscle loss is a potential downside of intermittent fasting.

Source: O’Conner, A. “A Potential Downside of Intermittent Fasting” www.nytimes.com September 28, 2020