Then we have the famous Matador study which was the first study to find an advantage to diet breaks (5). Unfortunately, a study being famous doesn’t make it a good study. This study had obese men diet either continuously for 16 weeks or diet for 2 weeks sandwiched with 2 week breaks for a total of 30 weeks.

The diet break group lost 4.3 kg more fat. They lost 50% more fat, but 50% more muscle. Nonetheless, the authors chalked this up to a metabolic advantage, but actual metabolic difference was merely 89 calories per day, nowhere near enough to explain the difference in weight loss.

In addition, the diet break group spent more time at maintenance which reverses any negative metabolic adaptations from dieting. The continuous group would experience the same thing if the researchers accounted for this.

But anyways, The Matador results don’t line up with their own data nor the results of every other study. A collection of studies (meta-analysis) found taking breaks has no advantage to continuous dieting, but wastes more time (6).

A more likely explanation for the Matador study was simply poor adherence. The study was done in obese men and the dropout rates were huge due to an astronomical 1000 calories deficit. No obese newbie dieter could sustain that for 16 weeks. In fact, the continuous dieting group lost the same fat until week 12 where they stopped eating their assigned deficit.

Technically, the diet breaks didn’t improve weight loss. You could say they improved adherence when using an extremely unrealistic method.

And even if the Matador study is somehow legit, would you really want to lose 50% more fat while sacrificing 50% more muscle and burning up 88% more time? The cost to benefit ratio is utterly poor even in the most questionable study.

Headland et al also conducted a pretty poorly controlled 1-year study comparing continuous dieting, diet breaks, and refeeds (7). The continuous dieting group lost the most fat at the end of the study and achieved greatest weight loss mid study despite starting at a pretty low body weight. The diet break and refeed group also had more dropouts because psychologically it’s hard to go back to dieting when you’ve halted the lifestyle.

There’s no consistency being built especially for dieting beginners. Clients tell me this all the time. They go off their plan and when trying to get back to dieting, they feel like they’re starting over. The mental obstacle later may not be worth the so-called mental relief of a diet break.

The more realistic a diet gets, the trend is clear, diet breaks aren’t worth the time.

Enter Siedler et al 2020, one of the best studies to date (8). They looked at continuous dieting vs diet breaks in strength trained females, a population that is much more adherent than obese populations. They used a realistic 25% deficit and matched for both protein intake and weekly exercise.