Intermittent fasting is an increasingly popular diet technique. Now a randomized controlled trial reports that at least one version of the method — time-restricted fasting — may have benefits.
In an eight-week trial, published in Cell Metabolism, scientists randomly assigned 58 obese men and women to three groups. The first ate whatever they wanted without counting calories, but only between 3 p.m. and 7 p.m. The second ate what they wanted between 1 p.m. and 7 p.m. The third, a control group, ate without restrictions.
In both of the groups that practiced time-restricted fasting, participants consumed an average of 550 fewer calories a day and lost about 3 percent of their body weight. Compared with the controls, both groups had significantly reduced fat mass, reductions in oxidative stress, and reductions in both fasting insulin and insulin resistance, which suggest a reduced risk for diabetes. Blood pressure, heart rate, cholesterol and triglyceride levels were unaffected.
Four participants in time-restricted fasting groups dropped out of the study because of scheduling problems, but none quit because they disliked the regimen. Five controls also dropped out.
“Our main finding here is that time-restricted fasting cuts out 550 calories a day, which is very hard to do in an ordinary calorie-restricted diet,” said the senior author, Krista A. Varady, a professor of nutrition at the University of Illinois, Chicago. “The coolest part is that it’s so simple. All you have to do is watch the clock.”
