Intermittent fasting can produce clinically significant weight loss as well as improve metabolic health, according to a new study review led by University of Illinois Chicago researchers.
“We noted that intermittent fasting is not better than regular dieting; both produce the same amount of weight loss and similar changes in blood pressure, cholesterol and inflammation,” said Krista Varady, professor of nutrition at the UIC College of Applied Health Sciences and author of “Cardiometabolic Benefits of Intermittent Fasting.”
According to the analysis published in the Annual Review of Nutrition, all forms of fasting reviewed produced mild to moderate weight loss, 1%-8% from baseline weight, which represents results that are similar to that of more traditional, calorie-restrictive diets. Intermittent fasting regimens may also benefit health by decreasing blood pressure and insulin resistance, and in some cases, cholesterol and triglyceride levels are also lowered. Other health benefits, such as improved appetite regulation and positive changes in the gut microbiome, have also been demonstrated.
The review looked at over 25 research studies involving three types of intermittent fasting:
Various studies of time-restricted eating show participants with obesity losing an average of 3% of their body weight, regardless of the time of the eating window.
Studies showed alternate day fasting resulted in weight loss of 3%-8% of body weight over three to eight weeks, with results peaking at 12 weeks. Individuals on alternate day fasting typically do not overeat or binge on feast days, which results in mild to moderate weight loss, according to the review.
Studies for the 5:2 diet showed similar results to alternate day fasting, which surprised the study’s reviewers. The subjects who participate in the 5:2 diet fast much less frequently than alternate-day fasting participants do, but the results of weight loss results are similar.
Weight loss in both the alternate day and 5:2 fasting are comparable to more traditional daily calorie-restrictive diets. And, both fasting diets showed individuals were able to maintain an average of 7% weight loss for a year.
“You’re fooling your body into eating a little bit less and that’s why people are losing weight,” Varady said.
Varady added the review set out to debunk some myths regarding intermittent fasting. Intermittent fasting does not negatively affect metabolism, nor does it cause disordered eating, according to the studies reviewed.
“Fasting people are worried about feeling lethargic and not being able to concentrate. Even though you are not eating, it won’t affect your energy,” Varady said. “A lot of people experience a boost of energy on fasting days. Don’t worry, you won’t feel crappy. You may even feel better.”
The study review includes a summary of practical considerations for those who may want to try intermittent fasting. Among the considerations are:
There are several groups who should not intermittent fast, according to the studies. Those individuals include:
“People love intermittent fasting because it’s easy. People need to find diets that they can stick to long term. It’s definitely effective for weight loss and it’s gained popularity because there are no special foods or apps necessary. You can also combine it with other diets, like Keto,” Varady said.
Varady has recently been awarded a National Institutes of Health grant to study time-restricted eating for 12 months to see if it works long term.
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