Obesity is a persistent public health problem in the United States, with almost 74% of U.S. adults 20 years and older classified as overweight or obese, according to data from the Centers for Disease Control and Prevention. Excess weight is associated with serious health consequences, including type 2 diabetes, cancer, and cardiovascular disease. Yet even among people who recognize the health risks, achieving and sustaining weight loss is a daunting task-and complicated by the wide array of popular diet regimens promising results.
Among them is intermittent fasting, an increasingly popular approach to weight loss that focuses on when food is consumed as well as how much. Although some previous research has shown intermittent fasting to be effective, until now there has been no synthesis of existing data to determine their overall quality and strength for generating clinical recommendations. A recent umbrella review of meta-analyses of randomized controlled trials on the topic, published in the December 2021 JAMA Network Open, aimed to do just that.
The researchers examined four different types of intermittent fasting: (1) zero-calorie alternate-day fasting, (2) modified alternate-day fasting, (3) fasting for one to two days per week (the 5:2 diet), and (4) time-restricted eating. They found that only two of the four types of fasting had statistically significant results for weight loss in overweight or obese adults-modified alternate-day fasting and the 5:2 diet. Modified alternate-day fasting was also associated with improvements in low-density lipoprotein cholesterol levels, triglycerides, and blood pressure in the first two to 12 months of dieting.
Because adherence to diets over a long period of time is often challenging for people trying to lose weight, the authors recommended additional research into strategies to improve adherence. They also noted that no type of fasting has shown a clear and sustainable clinical benefit, mostly because the trials so far were mainly conducted among healthy adults and for short follow-up periods. The authors called for additional trials with a broader participant pool, including adolescents and those older than 65 years, longer follow-up periods, and more attention to clinical outcomes such as cardiovascular events and mortality.-Gail M. Pfeifer, MA, RN