I know, it sounds a little crazy, but taking a break from your diet may actually help you lose more weight.
Part of the difficulty in losing weight, and maintaining that weight loss, is that the body responds through a series of compensatory changes – especially a reduction in resting energy expenditure.
Resting energy expenditure is largely determined by body size and composition (lean mass vs. fat mass). Therefore, we would expect it to decrease with weight loss. However, during periods of energy restriction, it reduces more than we might expect from changes in body composition – this has been referred to as “adaptive thermogenesis”.
This adaptation leads to a reduced efficiency of weight loss. For example, at the onset of a diet, weight loss occurs as expected form energetic calculations. However, as the diet continues, weight loss per unit energy deficit is reduced. So, finding a way to slow down this adaptation may improve weight loss and maintenance.
Some research done to date has suggested that many of these compensatory responses to dieting can be reversed following a 7-14 day period of energy balance (eating at weight maintenance calories). This leads us to believe that period of deliberately eating at maintenance calories can be exploited during dietary interventions to enhance the efficiency of weight loss in a way similar to periodization in exercise training programs to avoid overtraining.
The MATADOR (Minimizing Adaptive Thermogenesis And Deactivating Obesity Rebound) study was conducted in Australia on 51 obese males. Participants were randomly assigned to either a continuous (16 weeks of dieting) or intermittent (8 weeks of dieting + 2 week break + 7 weeks of dieting + 2 week break = 16 weeks of dieting, 30 weeks total) energy restriction group. Each group completed an 8-week post-weight loss weight maintenance phase as well so total length of intervention was 28 and 42 weeks, respectively (there was also a 4-week baseline period before the intervention).
Energy restriction for all groups was designed to be 2/3 of each individual’s weight maintenance caloric requirements (a 33% reduction in energy intake). Resting energy expenditure was measured every 4 weeks and calories were adjusted to maintain a 33% caloric deficit – the exception being the weight maintenance periods in which participants consumed 100% of their maintenance calorie requirement.
When it comes to weight loss, and especially fat loss, diets, composition of the diet plays a large part. The planned macronutrient distribution in both groups was 25-30% of calories from fat, 15-20% from protein, and 50-60% from carbohydrates.
GIVE ME A BREAK
Weight loss was found to be significantly greater in the intermittent dieting group than the continuous dieting group – about 50% greater at the end of the study and 80% greater 6-months after the study ended.
There was a significantly greater loss of fat mass in the intermittent dieting group than the continuous dieting group with non-significant changes in fat free mass between the two groups. In fact, fat loss plateaued by week 12 (of 16) in the continuous group and which was not observed in the intermittent group.
Reduction in resting energy expenditure did not differ between the groups, however, given the difference in weight loss between groups and after adjusting for changes in body composition, the reduction was significantly smaller in the intermittent group than the continuous group.
Six months after the study ended, both groups had regained some weight, but the intermittent group regained less than the continuous group (+7.7 lb vs. +13.0 lb on average).
The MATADOR study results are in contrast with the majority of published research showing no advantage of intermittent over continuous dieting. Note that intermittent dieting is NOT the same thing as intermittent fasting, a practice of abstaining from eating for an extended period of time and eating within a shorter feeding window. At best, recent reviews have shown intermittent dieting (primarily in the form of intermittent fasting) being equivalent, but not superior, to continuous dieting.
Weight regain following weight loss is common, as is the difficulty of continued weight/fat loss in an extended dieting period.
Anecdotally, I have seen more nutrition coaches implementing “diet breaks” with their clients with great success. I believe that this is, in part, due to at least partial hormonal reset from eating at maintenance calorie intake for 1-2 weeks (a physiological response) and also due to the psychological benefits that eating at a higher calorie intake brings to the dieter – thus leading to greater overall compliance, which is ultimately the determining factor when it comes to weight loss success.
If you are planning to embark on a fat loss phase, or have been dieting for some time already and have hit a plateau despite lowering calories and/or increasing energy expenditure, perhaps you would benefit from a planned diet break.