“It's not a miracle solution.” Intermittent fasting is no more effective than traditional diets, a new study shows

Intermittent fasting, heavily promoted in recent years as a weight loss solution, is no more effective than traditional diets and barely beats the results obtained without any change in diet, according to an extensive analysis of data from several studies, writes The Guardian.

Researchers analyzed data from 22 studies worldwide and found that overweight or obese people lost about as much weight following classic dietary recommendations as when they adopted intermittent fasting, such as Michael Mosley's “5:2” method, which severely restricts calorie intake for two out of seven days.

In addition, the difference from no diet for weight loss was modest, according to the analysis. On average, participants lost only about 3 percent of their body weight through intermittent fasting, below the 5 percent threshold doctors consider clinically relevant. All included studies were short-term, looking at outcomes for no more than 12 months.

“Intermittent fasting is not a miracle solution, but it can be one of several options for weight control,” said Dr. Luis Garegnani, lead author and director of the Associated Cochrane Center at the Italian Hospital in Buenos Aires, Argentina. “Intermittent fasting probably produces similar results to traditional dietary approaches to weight loss. It doesn't seem clearly superior, but it doesn't seem inferior either,” the specialist said.

Intermittent fasting has become very popular

Intermittent fasting involves either restricting food at certain time intervals, or alternating days of normal eating with days of fasting. Its popularity has exploded, amid promises that it would help not only to lose weight, but also to improve physical and cognitive health or even to slow down aging, notes the British publication.

The experts used reference methods for the analysis done in evaluating data from randomized clinical trials that included 1,995 adults from Europe, North America, China, Australia and South America. Several forms of intermittent fasting have been looked at, such as every other day, the 5:2 diet, where people fast two days a week, and time-restricted eating.

Beyond modest weight loss benefits, researchers found no strong evidence that intermittent fasting improves quality of life more than other types of dieting.

Garegnani stressed that it is important to clarify the evidence, in the context of the intense promotion of intermittent fasting in the press and online. Many of the existing studies are of short duration and of modest quality, making it difficult to draw firm conclusions about real benefits.

Surprisingly, none of the 22 studies asked participants how satisfied they were with intermittent fasting, Garegnani added.

What complicates the analysis

Dr Zhila Semnani-Azad, from the National University of Singapore, explained that the effects of fasting could depend on when it is practiced, given the close connection between circadian rhythms and metabolism.

Animal studies suggest that fasting can alter the way fat stores are used, improve insulin sensitivity, which is relevant in diabetes, and reduce inflammation and oxidative stress.

It could also stimulate a process called autophagy, the mechanism by which the body “recycles” cellular components, possibly with effects on longevity. However, the lack of a universal definition of intermittent fasting makes it difficult to compare studies and understand its real impact, she added.

For his part, Maik Pietzner, a professor of health data modeling at the Health Institute of the Charité University Hospital in Berlin, said he was surprised that the weight loss was modest from intermittent fasting compared to no action at all.

But he pointed out that the data aligns with other evidence that intermittent fasting people are often less physically active and that weight loss is difficult to achieve without medication.

“Possible moderate weight loss”

In his own research, short periods of complete fasting, even as little as two days, had minimal effects on the body. In a study where participants consumed only water for seven days, significant changes in blood proteins only appeared after three days.

“If people feel better following such regimens, I wouldn't stop them. But this review, along with other research in the field, makes it clear that there is no strong evidence for positive effects beyond possible modest weight loss,” Pietzner said.

“Our body has evolved in conditions of food scarcity and can cope very well with prolonged periods without food, but that does not mean that we function better once these mechanisms are activated,” the professor said.