A New Study Shows Intermittent Fasting Doesn’t Actually Do What We Thought It Did

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Intermittent fasting has become a very popular method of “dieting” over the last several years. The concept? Don’t focus on what you eat, but rather when you eat. Common practice includes a strict 16-hour fasting period between meals, so if you ate dinner at 7:00 p.m., you wouldn’t eat again until 11:00 a.m. the following day. For some, this cycle fits naturally into their existing routine; for others, it’s nearly impossible.

Though many experts have touted intermittent fasting as a successful weight-loss tactic, a randomized clinical trial conducted by researchers at the University of California San Francisco—and recently published in JAMA Internal Medicine—proves otherwise. Beginning in 2018, the team recruited 116 men and women ages 18 to 64 who were overweight or obese and divided them into two groups. Over the course of 12 weeks, one group was assigned to skip breakfast and eat at their own leisure between noon and 8:00 p.m., and the other (the control group) ate three structured meals at normal meal times, as well as snacks. Both groups exercised as they normally would, and it was tracked by the researchers using a Bluetooth-connected scale.

The findings, which have greatly surprised proponents of intermittent fasting, revealed an average loss of 2 pounds for the first group and 1.5 pounds for the second, respectively—the difference between the two is a mere 0.42 percent. Another interesting discovery: Those who engaged in time-restricted eating seemed to lose more muscle mass than those who ate as they pleased. However, the team has indicated this area of testing requires further study.

Nutritionist Jennifer Hanway says this new study illustrates what most nutritionists and dietitians have been saying for years: “Intermittent fasting is just another way to restrict calorie intake and is not a long-term strategy or ‘magic pill’ for healthy weight loss. While there have been some small, short-term trials using human subjects following a 16:8 fasting pattern that show short-term weight loss, when compared against trials that study overall calorie restriction, we see similar results.”

According to Hanway, it’s also important to understand that nutrition studies can be flawed in their methodology, as there are other lifestyle variables, such as stress and medications, that are not typically controlled for. “The majority of nutrition studies are self-reported.”

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