How Diet Breaks Affect Metabolism

Diet Breaks May Offer More Psychological Benefits than Metabolic

Diet breaks may be more effective than previously thought in counteracting the negative effects of long-term dieting.

If you’ve hit a weight loss plateau or are experiencing adverse effects of a strict low-calorie diet, it might be time to consider a diet break. As the name suggests, a diet break involves taking a break from your diet to temporarily increase your calorie intake to maintenance levels, typically for one to two weeks.

Emerging research suggests that diet breaks do more than provide a mental and physical reset. They could also help counteract the slowdown in metabolic rate that often accompanies long-term dieting.

Previous research explored how diet breaks might counteract metabolic slowdown. A 2018 MATADOR (Minimizing Adaptive Thermogenesis And Deactivating Obesity Rebound) study found that participants who alternated between two weeks of dieting and two weeks of eating at maintenance calories over 30 weeks experienced several benefits.

These included improved fat-loss efficiency, preservation of lean body mass, and minimal metabolic rate decline. They also regained less weight than a group that followed continuous dieting for 16 weeks.

Due to their alternating schedule, the intermittent dieters required more time (30 weeks) to complete the equivalent of 16 weeks of calorie deficit. The results showed that diet breaks significantly reduced metabolic adaptation — slowing metabolism as people lose weight, mainly because their bodies carry less mass.

Subsequent research has presented mixed findings. Some studies reported mild benefits from diet breaks, while others observed no discernible effect.

This prompted a recent meta-analysis to provide a clearer consensus by examining studies on diet breaks and refeeds — periods of eating at or above maintenance calories. A meta-analysis published in January 2025 examined whether diet breaks can mitigate metabolic adaptation during weight loss.

The findings found intermittent dieting caused only a slight difference in metabolic rate compared to continuous dieting. Specifically, groups incorporating diet breaks or refeed days experienced a metabolic rate drop of about 50 calories less than those on constant calorie restriction. Across these studies, participants generally lost about 5% of their body weight.

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References

1. Byrne, N. M., Sainsbury, A., King, N. A., Hills, A. P., & Wood, R. E. (2018). Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. International journal of obesity (2005), 42(2), 129–138. 1
2. Poon, E. T., Tsang, J. H., Sun, F., Zheng, C., & Wong, S. H. (2025). Effects of intermittent dieting with break periods on body composition and metabolic adaptation: a systematic review and meta-analysis. Nutrition reviews, 83(1), 59–71. 2