Intermittent fasting: new research questions its effectiveness

CNN
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Intermittent fasting is one of the many trendy ways people try to lose weight or keep it off.

This practice, also known as time-restricted eating, is a weight loss method in which you limit your eating hours to set times (usually 8 hours out of 24 hours) and consume only clear liquids for the remaining 16 hours. Another method is to fast for 2 or 3 days during the week or month.

How effective is intermittent fasting? work?

Previous research showed the benefits Until the time limit.a December 2019 review Many human and animal studies have found benefits of restricting calories to short periods of the day, including improved longevity, lower blood pressure, and weight loss. (However, many of those studies were in mice; the human studies were much shorter, lasting just a few months.)

However, for one year, Research to be published in April 2022 A study that tracked 139 overweight to extremely obese Chinese adults found that calorie counting was no more effective at improving weight loss or cardiovascular health.

Research published this week suggests that eating within 8 hours is significantly associated with a 91% increased risk of death from cardiovascular disease when compared to eating over 12 to 16 hours, prompting immediate medical attention. Aroused questions and criticism from home. period.

The following is a summary of preliminary research that has not yet been peer-reviewed or published. Presented on Monday in chicago At an American Heart Association conference.

“We were surprised to learn that people who followed an 8-hour time-restricted eating schedule were more likely to die from cardiovascular disease,” said lead study author Victor Wenze Zhong, a professor of epidemiology. Professor, Department of Biostatistics) said. School of Medicine, Shanghai Jiao Tong University, China.

“Our findings encourage a more careful and individualized approach to dietary recommendations, ensuring they are consistent with individual health conditions and the latest scientific evidence,” Zhong said. said in a statement.

To analyze the health status of U.S. adults over time, a new study analyzed data from 20,000 people who answered 24-hour dietary questions during the first year of enrollment, then looked back at death records for several years afterward. Ta. .

The analysis showed an association between the 8-hour eating window and deaths from cardiovascular disease, but the authors said they could not determine whether this dietary pattern was a cause of death.

Many experts express concern About new research.

Kevin McConway, emeritus professor of applied statistics at Britain's Open University, said: “There is enough in the conference abstract to raise big questions about whether this study can show what it sets out to show.'' ' study.

“The researchers categorized people into different eating patterns based on what and when they reported eating over just two days over an average eight-year study period,” McConway said in a statement. “Relating these patterns to intentionally long-term, time-restricted dietary interventions appears to be well beyond the data.”

Tom Saunders, emeritus professor of nutrition and dietetics at King's College, London, who was not involved, said in a summary that people who follow time-restricted diets, truck drivers, night workers and health professionals He also did not say whether he worked “anti-social” hours, as he often does. In this study.

“This is important because there is evidence that these types of work practices are associated with increased risk of type 2 diabetes and CVD (cardiovascular disease),” Sanders said in a statement.

Duane Mellor, a registered dietitian and senior teaching fellow, said there is no summary information on things like tobacco and alcohol use, physical activity, or poverty levels among people who say they practice intermittent fasting, all of which are linked to heart disease. He said that it is a risk factor. Aston Medical School, Birmingham, UK. Mellor was not involved in the study.

“We must be very careful not to generate worrying headlines and articles based on such limited information,” Mellor said in a statement. “What he eats and his overall lifestyle are probably more important than whether he has eaten all his food within eight hours in two days over the past 10 years.”

As with many investigations in science, research can yield contradictory results. It often depends on the quality of the studies and whether they all measured the same thing in the same way.

In the case of fasting, experts say research is extensive, with some studying fasting for more than two days a week and others looking at fasting from 8 a.m. to 4 p.m. Some people are also researching fasting from noon to 8 p.m., or at other times.

“In my opinion, this data is not very convincing for intermittent fasting. It's hard to study and publish clean results,” nutrition researcher Christopher Gardner told CNN's Principal Speaking to medical correspondent Dr. Sanjay Gupta.

“And they don't focus on quality, right?” said Gardner, a medical research professor at the Stanford Prevention Research Center in Palo Alto, California. “I'm worried that people will say, 'This is the window, so I can eat a pint of ice cream, I can eat a cookie, I can eat whatever. Because it's a thing.'' It's a window. ”

Experts say what and how much you eat is more important than anything else.

“Ultimately, the determining factor for weight loss, reductions in body fat, visceral fat, blood pressure, blood sugar and lipid levels is a reduction in caloric intake, regardless of the distribution of food and drinks consumed throughout the day. It depends,” said Alice Lichtenstein, director and senior research scientist at the Cardiovascular Nutrition Institute at Tufts University. He told CNN in a preliminary interview. She was not involved in the study.

moreover, September 2020 A randomized clinical trial of 116 people (considered the gold standard in research) found a significant difference in weight loss between those who restricted their diet from 8pm to noon the next day and those who did not. was not seen.

Also, Observational study in January of 547 people — Again, the results showed no real difference between the two. Lose weight by restricting meal times.