The Fortnight Diet: A Boon to Long-Term Weight Loss?


To increase the likelihood of successful long-term weight loss, this twist on a calorie-restricted diet may be worth trying: Alternate two weeks on the diet with two weeks off. This was tested in a small Australian study oddly called MATADOR (Minimizing Adaptive Thermogenesis And Deactivating Obesity Rebound), published recently in the International Journal of Obesity. Researchers from the University of Tasmania put 19 obese men (ages 25 to 54) on a 16-week continuous diet. All meals were provided, and the men’s usual calorie intake was reduced by one-third. Another 17 obese men were put on the same calorie restricted diet but for two weeks at a time, alternating with two week “rest periods” of their customary eating, for a total of 16 weeks of dieting over 30 weeks.

The intermittent dieters not only lost more weight than the continuous dieters (31 vs. 20 pounds), but they regained less weight (7 vs. 13 pounds) during the six months after the end of the diet, so they ended with a 17-pound greater weight loss, on average. It’s well known that prolonged calorie restriction causes the body to reduce its resting metabolic rate to conserve energy (this is called the famine reaction or adaptive thermogenesis), thus burning fewer calories.

That’s one reason why most weight-loss diets fail in the long term. The researchers hypothesized that two-week cycling on and off the diet lessened this compensatory biological change. In contrast, they pointed out, popular diets that alternate one, two, or several days of complete or partial fasting with days of “feasting” have been found in studies to be no more effective than conventional continuous dieting.

It’s not known if results would be similar in women, or if weight loss would be as great in real-world conditions (that is, when dieters are not supplied all of their calorie-restricted meals). “While additional work is needed to further investigate the mechanistic bases for this novel intermittent approach, these findings provide preliminary support for the model as a superior alternative to continuous energy restriction,” the researchers concluded.