Stopping food intake for some time would not bring the desired benefits.
Whether to criticize or praise it, much has been saying recently about the implications that intermittent fasting diets -that is, going a certain number of hours or even days of the week without eating- could bring when it comes to losing weight.
However, despite what many experts claim when recommending it, a new study (one of the first to analyze the effects of fasting and energy restriction in thin people) provides not very encouraging evidence, since it indicates that this type of diet would offer fewer benefits for fat reduction than a traditional diet.
Specifically, the three-week randomized trial involving 36 participants concluded that an alternate-day intermittent fasting program offers less fat-reducing benefits than a classic combined diet, which restricts daily energy intake.
Ultimately, one of the most important implications of the study is to demonstrate that alternate-day fasting may not offer specific metabolic or health benefits of that practice compared to a standard daily diet.
Recall that one of the issues for which this diet is recommended is the possibility of triggering an energy metabolic shift that, in addition to promoting weight loss, is associated with greater longevity and a lower incidence of disease, including cancer and obesity.
As indicated, intermittent fasting involves alternating periods of voluntary fasting with others in which food is ingested. There are many ways to carry it out, with different schedules, ranging from abstaining from food for part of the day to the popular 5:2 diet (eat 5 days a week and fast 2 days) to alternate-day fasting (eat one day, fast the next).
Many adherents of this nutritional model claim that fasting schedules are relatively easy to adopt and adhere to, and theories suggest that fasting may trigger beneficial changes in metabolism that promote weight loss.
However, few studies have examined the specific effects of intermittent fasting or compared its effects with diets that simply reduce daily net calories.
Iain Templeman-from the Center for Nutrition, Exercise, and Metabolism at the University of Bath Department of Health-and colleagues recruited 36 lean participants and divided them into 3 groups of 12, who followed different diets for 3 weeks.
The first group followed a restricted fasting diet on alternate days, consuming 150% of their usual daily energy intake only on certain days.
The second group followed a non-fasting diet of an equal amount of energy with 75% daily energy intake, which would represent a classic diet in which the amount of calories ingested is reduced.
And the last group followed an alternate-day fasting diet with no restriction in energy intake, which would translate to 200% daily energy intake on alternate days.
After 3 weeks, the second group showed the greatest weight losses, with an average fat decrease of 1.57 kg. Meanwhile, the first alternate-day fasting group lost fat less effectively (an average of 0.74 kg), and the latter group showed no significant drops in either weight or fat.
Other studies showed that there were no significant differences in cardiometabolic health, metabolic molecules, or gene expression in fat cells among the 3 groups.
Templeman noted that alternate-day fasts tended to be less active days when compared with those participants had before starting the diet, which could be a factor affecting fat loss.
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