Should you be using diet breaks for fat loss?
Take-aways
Taking diet breaks resulted in similar fat loss, weight loss and improvements in waist circumference as being in a continuous deficit.
However, diet breaks may attenuate metabolic adaptation/reductions in resting metabolic rate slightly, facilitating long-term weight loss and weight loss maintenance.
The way I see diet breaks is as a “neutral to very slightly positive” diet strategy. It is by no means a must, and adherence is paramount. If diet breaks fit well into a client’s lifestyle and preferences, we incorporate them. If not, there is minimal harm done.
A simple way to incorporate diet breaks is to simply consume maintenance calories during deload weeks.
If you’re not up to speed on what that means, let me break it down. When you’re losing weight, you can either stay in the exact same calorie deficit throughout your whole diet phase (say, a consistent 500 kcal deficit, daily) or you can manipulate the size of that deficit over time, such that you have the same average daily deficit (still 500) but you have days with higher and lower calorie intakes. The former approach is what is called “continuous energy restriction” (CER) and the latter approach is what is called “intermittent dieting with break periods” (INT-B).
Ultimately, the two should lead to similar weight loss (the law of conservation of energy), but they could lead to differences in how much muscle you retain, for example, if you’re able to set your diet up in a way that facilitates effective training. Or, it could lead to a more sustainable diet, by fitting into your lifestyle better and allowing you to be more flexible on certain days vs others.
That’s what this study sought to examine. They included 12 randomized controlled trials that compared CER to INT-B on a calorie-equated basis. Here’s what they found.
Most outcomes were similar between groups. Specifically, both CER and INT-B led to significant and statistically similar improvements in weight loss, fat loss, body fat percentage and waist circumference.
However, diet breaks did seem to lead to lower metabolic adaptation (essentially, your body’s propensity to reduce energy expenditure in response to you trying to lose weight). Specifically, reductions in resting metabolic rate during the diet - the amount of energy your body expends at rest - were significantly smaller when taking diet breaks vs using a continuous approach.
Now, the difference wasn’t particularly large - and probably won’t influence your diet too meaningfully either way - but it is worth noting.
The way I typically incorporate diet breaks is to eat at maintenance during deload weeks whenever I am in a fat loss phase. Since the goal of a deload week is to promote recovery, eating at maintenance is beneficial. Likewise, deload weeks should probably occur every 6-12 weeks, which might be a good frequency for a diet break.
