A new randomized clinical trial published October 15 suggests intermittent fasting may help people lose slightly more body fat—but there’s a catch. Participants who limited eating to eight hours daily lost approximately 2.4 pounds more fat than those who simply reduced calories.
The study, published in the British Journal of Nutrition, found that the additional fat loss did not translate into significantly greater overall weight loss. Researchers also identified a potentially concerning change in metabolism.
Related: What Time-Restricted Eating Does to Your Body, According to Experts
An Eight-Hour Eating Window Made a Difference
The MACRO randomized clinical trial followed 100 adults ages 20 to 60 with severe obesity for 12 weeks. Researchers assigned participants to two calorie-restricted diets, with both prescribed approximately 60% of their estimated daily energy expenditure.
One group consumed meals between 10 a.m. and 6 p.m. The other reduced calories without following a restricted eating window.
By the end, the fasting group had lost approximately 7.7 pounds of fat, compared with 5.3 pounds in the conventional calorie-restriction group.
However, total weight loss was similar: approximately 9.5 pounds versus 8.4 pounds, respectively.
The distinction matters because losing body fat and losing overall body weight are not necessarily the same thing. Researchers measured body composition using DXA scans rather than relying exclusively on bathroom-scale readings.
Related: Why You’re Not Losing Weight Eating ‘Healthy,’ According to Dietitians
Researchers Found a Potential Metabolic Drawback
The additional fat loss came with another finding: participants practicing time-restricted eating experienced a greater decline in resting metabolic rate, the energy their bodies burn at rest.
The researchers concluded that combining fasting with calorie restriction “does not enhance weight loss,” despite the modest improvement in fat-mass reduction.
They also reported evidence suggesting greater metabolic adaptation, which could complicate efforts to maintain weight loss over time. However, the study lasted only 12 weeks, so long-term outcomes remain uncertain.
The findings reinforce an important distinction. Intermittent fasting may help some people structure their eating, but a shorter eating window is not automatically a superior weight-loss strategy.
For readers considering fasting, the practical question is whether the schedule makes balanced eating and a sustainable calorie deficit easier.
Related: Scientists Put Mice on a Vegan Diet and Noticed Something New Within Just Days
