The Reason Intermittent Fasting Doesn't Work

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Intermittent fasting has become one of the most popular weight-loss interventions of the last couple of years, but a 2020 study has revealed that the practice "is not more effective in weight loss than eating throughout the day."

When compared to eating three meals a day, fasting for 16 hours was found to give no significant benefits in terms of losing weight or improving metabolism. The study suggested that "other interventions" were still required to shave off the pounds and that relying solely on 16/8 intermittent fasting was not enough to do the trick.

What The Study Uncovered

While past research amply supported the benefits of intermittent fasting in keeping weight under control and maintaining a healthy lifestyle, a new study led by Dylan A. Lowe of the University of California's Cardiovascular Research Institute In San Francisco uncovered that time-restricted eating (TRE) only brought about a "modest decrease in weight."

The findings, published in September in the Journal of the American Medical Association (JAMA), unveiled that the weight loss achieved through TRE "was not significantly different" from the results of the control group, who was instructed to eat throughout the day.

Intermittent Fasting VS Eating Three Meals A Day

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In their efforts to explore the differences between TRE and consistent meal timing (CMT) -- three meals a day plus snacks if required -- Lowe's team enlisted 116 volunteers with overweight or obesity, of whom 70 were men. The participants, aged 18 to 64, were divided into two groups and were tracked for a period of 12 weeks, during which time the scientists monitored their weight and metabolic markers, such as glucose, insulin, blood pressure, hemoglobin, LDL cholesterol, and triglycerides.

While the CMT group was not subject to any dietary restrictions, the TRE group was instructed to only eat between 12 pm and 8 pm.

Only A 1.7 Percent Weight Decrease In 12 Weeks

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The results showed only a 1.17 percent weight decrease with intermittent fasting over the course of 12 weeks, on top of a small decrease in lean mass. At the same time, the team reported a 0.75 percent decrease in weight in the control group, pointing to no significant difference in weight loss or metabolic benefits between CMT and TRE.

"Time-restricted eating, in the absence of other interventions, is not more effective in weight loss than eating throughout the day," concluded the study authors.

However, Diet Doctor's Dr. Bret Scher cautions that these results should be interpreted with care. In a recent article, Scher argued that certain factors may have contributed to the inefficacy of TRE in this particular case.

It's Not For Everyone

According to Scher, the TRE group in Lowe's study was only given a time interval in which to eat but didn't receive any coaching regarding calorie intake, how to choose nutrient-rich food, and how much to eat. By testing equal calorie diets for both groups, the study eliminated TRE primary benefit, which is to provide "an effective means of reducing daily calories," said Scher.

As he pointed out, what the study actually proved "is that 16 hours of TRE starting at 8 pm, with no control for diet quality and no reduction in calories, does not lead to weight loss or metabolic benefits for the majority of people."

Nevertheless, this doesn't mean that intermittent fasting can't help with weight loss at all, Scher argued.

"It’s true that fasting, even as short as 16 hours, will trigger hunger and cravings in some people, leading to increased snacking, more overall calories, and worse food quality."

"But for those who can fast, reduce their overall calories, and continue to eat nutritious food that doesn’t cause insulin and glucose 'spikes,' it is likely another story," Scher noted in his article.