Wednesday, May 20, 2015

Losing Weight With Exercise (Only) - Chances That This Will Work are Excellent... if You are Young and Fat... and Lazy!

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?
The idea that you can lose weight only by working out (most people even think of "cardio") is as hilarious as it is ingrained in the Western cultural believes. In fact, the fact that some studies indicate that overweight individuals end up losing weight when they are (often put) on an exercise regimen, however, does not mean that their workouts "pulled the trigger". Rather than that, their ability to lose weight is a consequence of an incomplete compensation of the extra-energy expenditure... and yes, I am talking about calories in vs. calories out here, because, in the end, the energy balance is what counts - even if energy intake and output must not be seen as independent quantities (learn more).

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?
If you exercise too much and don't compensate you are steering towards the Athletes Triad.

Female Athletes' Body Comp Suf- fers From Dieting

Female Athlete's Triad is not ex- clusively female

Female Athlete's Triad - A Vicious Cycle

Female Athlete's Triad - Recovery Part 1/3

Female Athlete's Triad - Recovery Part 2/3

Female Athlete's Triad - Recovery Part 3/3
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:
    What both equations have in common is the fact that a constant coefficient is divided by the duration in days. In other words: The longer people exercise, the more they compensate, the lower the exercise-induced energy deficit.
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) 
    As you can see in Figure 1, fat, young individuals benefit most from exercise. Initially, they don't compensate at all for the extra-energy expenditure, but rather reduce their energy intake for every 1kcal/day they burn by another 2kcal/day (that's why the graph starts at - 200%).
  • 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.
The most important message, however, is the fact that the longer you train (=adhere to an exercise regimen, not "60 min vs. 20 min"!), the more you tend to compensate for the extra energy you burn.
Always hungry? Can't lose weight? "Train more and eat more" (to maxi-mize your energy flux) could be the solution, says study on the influence of energy flux on appetite and metabolic rate while dieting | read more
Bottom line: Despite the fact that the authors conclude that "for studies of longer duration (about 80 weeks), the energy compensation approached 84%", it appears obvious that the currently available evidence does not fully support the idea of "diet-less" long-term weight loss with exercise.

This appears to be specifically true for those who are already normal-weight or old. For these individuals the data in Figure 1 clearly indicates that even in the "most productive" early weeks of an exercise regimen, any potential exercise-induced weight loss is stalled by an increase in food intake which (over-)compensates the extra increase in energy expenditure due to an increase in physical activity.

Speaking of which: Eventually, you do not exercise to be able to eat more (if you're still doing that you're a moron with an eating disorder and it's your fault you don't see those abs you keep asking me about in emails and messages on facebook), but rather to make sure that the weight you lose is fat, not muscle. If you keep that in mind when you're designing your workouts and diet plans you can easily avoid most of the fallacies of "losing weigh" | Comment on Facebook!
  • Riou, Marie-Ève, et al. "Predictors of Energy Compensation during Exercise Interventions: A Systematic Review." Nutrients 7.5 (2015): 3677-3704.