Author: Cait Callahan

Diet breaks are a highly discussed topic within the fitness industry, this strategy may be particularly appealing as it may allow ones metabolism, hunger, and mental state a “break” from dieting. Although there are many benefits to this approach, there are some caveats that should be discussed and practical measures that need to be considered in order to implement this strategy effectively. The purpose of this article is to give some guidance as to where “diet breaks” come from, why they are implemented, and how they can be applied throughout ones fat loss journey.

The idea of a diet break strategy comes from the MATADOR study (Minimizing Adaptive Thermogenesis and Deactivating Obesity Rebound) where an obese male population (25-54 years old, weight stable, and sedentary) was examined across a 16-week diet intervention. The subjects were randomly split into a continuous dieting group or an intermittent dieting group. Each group dieted for a total of 16 weeks and implemented a 33% calorie deficit. The difference between the groups being that the intermittent energy restriction group dieted for 2 weeks straight followed by 2 week “breaks” to their maintenance calories while the continuous group dieted for 16 weeks straight.

The goal of the study was to minimize adaptive thermogenesis (i.e., the magnitude to which resting energy expenditure decreases as a result of decreased body mass). Investigators hypothesized that an intermittent approach to energy restriction that also implemented periods of energy balance would minimize the extent to which adaptive thermogenesis was observed. Overall, this would provide an alternative approach to weight loss in a more sustainable manner minimizing the rebound effect observed after a dieting phase.
So, what did they find? Well, weight loss was significantly greater in the intermittent group than the control group and respective to total weight lost, the intermittent group lost more body fat while maintaining lean body mass and taking a smaller degree of adaptation to their resting energy expenditure. The study also took follow up data 6 months after the end of the intervention. What they found was that the amount of weight lost from baseline remained greater in the intermittent group. Specifically, the intermittent group lost on average 8.1 kg more than the control group at the period of follow up measurements. This supports the idea that implementing periods of energy balance may also aid in the ability to keep off weight that is lost during a dieting phase.

With all things considered, there is one very important piece to point out and that is the idea of maintenance calories. When utilizing a diet break approach that does not mean simply eating whatever you want when one is on “break”. It is still a calorie-controlled period based on what your maintenance is predicted to be. To determine this, increasing calories by 150-300 calories and paying attention to biological feedback will be important (scale weight fluctuations for example). It’s also important to note the population used in this study, many of you reading this are probably resistance-trained and may not have great amounts of body fat to lose. As such, the rate and the amount of loss should not be directly compared with the results of this study. For a resistance-trained person with healthy body fat levels, a half a pound to a pound per week in a deficit is a good rate of weight loss. Any faster rate of loss may be compromising muscle mass, which is certainly not desirable. Lastly, it is important to be adherent during any type of tracking phase; extra bites, not using a food scale, and estimating food while eating out will ultimately impact energy balance. Being aware of these choices and setting realistic expectations going through a dieting or maintenance phase is critical.

If an individual is looking to lose body fat without prolonged periods of energy restriction while minimizing the impact a deficit may have on resting energy expenditure, then the current literature would suggest that implementing an intermittent approach to dieting may provide better results while minimizing the rebound coming out of a diet. While the idea seems promising, there is still much research needed in trained populations to better assess just how practical this is in athletes that are physique oriented.

STUDY: Byrne NM, Sainsbury A, King NA et al.: Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study. Int J Obes (Lond). 2017.