|Wouldn't it be great if Taubes was right and you could sit your lazy flat-ass even flatter without having to worry to miss a chance of losing weight?|
So, if exercise will only help you lose weight, if you don't fully compensate for the exercise induced extra-energy expenditure, the obvious and important question is: What determines to which extent the extra-energy that's consumed by your muscles during physical activity is compensated for?
In a recent systematic review, Marie-Ève Riou and colleagues tried to answer this very question. To do so, they reviewed the contributions of sex, age, initial adiposity, as well as duration, dose, frequency and intensity of exercise in 61 studies with a total of 928 subjects. And what the researchers from the University of Ottawa found is a complex conglomerate of data that requires careful consideration and interpretation.
- Firstly, the overall mean energy compensation was 18% ± 93% - This may suggest that the average subject lost weight, but with a margin from -75% to 111% that's far from significant. And still, on average, the data indicates that exercise does not make those who get off the sofa and move their a$$ more hungry (one has to keep in mind, though, that not all of the studies allowed their subjects to eat as much as they wanted; in some cases where the energy compensation is negative, the subjects were simply required to diet)
- The analyses indicated that 48% of the variance of energy compensation is explained by the interaction between initial fat mass, age and duration of exercise interventions. The scientists even came up with an equation to determine the energy compensation in % for young and old individuals, respectively:
Warning! You must not forget, that the duration and extent of an energy deficit will also determine the degree of "metabolic shutdown", or, as I prefer to say, "metabolic compensation" that will occur in form of a reduction of your resting metabolic rate. If you take this into account, a dietary compensation of 80% after say 40 weeks may well fully compensate the remaining energy deficit which has melted away due to the metabolic slowdown.
- It's also interesting to take a look at the more complex graphs of a model that includes the other two previously mentioned parameters: Age and fat mass at the beginning of the study.
Figure 1: Fat mass (FM), age, duration of the exercise intervention and degree of energy compensation (100% compensation = no energy deficit, -200% = sign. appetite suppression + huge deficit | Riou. 2015)
- Sex, frequency, intensity and dose of exercise energy expenditure were not significant predictors of energy compensation. This is a bit surprising, as previous studies had suggested that women may be a bit more susceptible to exercise induced overeating (=overcompensation) than men, and that HIIT may less prone to cause people to compensate for the extra-energy they burnt than longer duration steady state exercise, but obviously these effects haven't been consistently observed in the studies the scientists reviewed.
- Riou, Marie-Ève, et al. "Predictors of Energy Compensation during Exercise Interventions: A Systematic Review." Nutrients 7.5 (2015): 3677-3704.