Intermittent fasting refers to a series of practices in which people restrict themselves to food for a few days a week or for part of each day. In recent years, such diets have become very popular.
Previous studies on intermittent fasting have yielded mixed results. They usually confirmed its safety and showed efficacy comparable to that of a calorie-restricted diet. Studies have been conducted for different types of fasting (1, 2).
In the new work, the scientists wanted to clarify if there is any specific benefit that intermittent fasting can bring to the body, but does not provide caloric restriction of the diet. Its participants were divided into three groups. In the first group, the volunteers fasted every other day, but on the day that followed the fast, they ate 100% more than usual. The second group followed a similar regimen, but after fasting, the participants ate 50% more. In the third group, the calorie content of the daily diet was reduced by 25%. None of the volunteers suffered from obesity.
The number of calories in the diet of participants in the second and third groups decreased to the same extent. In the third group, people received about the same amount of energy as before.
After four weeks, in the non-starving group, the participants “lost” an average of 1.9 kilograms, almost all of the weight loss was due to a decrease in body fat.
People who got the same number of calories, but fasted every other day, lost about 1.6 kilograms, but half of this weight was due to muscle tissue.
Weight loss in the “starving” group, who ate twice as much every other day, was extremely insignificant. That is, without calorie restriction, it was not effective.
“Many people believe that fasting diets are especially effective for losing weight, or that they have particular metabolic benefits, even without losing weight. However, our study suggests that there is nothing special about it compared to more traditional diets, ”said Professor James Betts of the University of Bath, lead author of the study.
Scientists emphasize that when fasting, it is especially important to remember that it can lead to a decrease in muscle mass. In addition, fasting can make it difficult to maintain a good level of physical activity, which can affect your health in the future.