|Sane caloric deficits (maybe 15-20% and thus more than in the study at hand) + strength training may facilitate recomp = body fat loss + muscle gain/maintenance.|
Now, a recent study from the University of Ottawa clearly suggests that, "despite an increase in fat-free mass [...] 6 months of aerobic, resistance, or combined training [adherence was controlled for] did not increase RMR compared [...] in adolescents with obesity" (Alberga. 2017).
In view of the energy thirst of your muscle and organ mass (total lean mass) this result seems odd. Needless to say that it is thus worth taking a look at the studies goals and methodology. As far as the first is concerned, the articles write that they started with the (logical) hypothesis that "resistance exercise training performed alone or in combination with aerobic exercise training would increase [the] resting metabolic rate (RMR) relative to aerobic-only and nonexercising control"(Alberga. 2017) groups.
In their subjects, postpubertal adolescents (N = 304) aged 14–18 years with obesity (body mass index (BMI) ≥ 95th percentile) or overweight (BMI ≥ 85th percentile + additional diabetes risk factor(s)), who were randomized to 4 groups for 22 weeks however, the scientists did not observe the expected increase in RMR in response to the four weekly sessions of ...
- Aerobic exercise training - Participants exercised on treadmills, cycle ergometers, and/or elliptical machines at an intensity of 65%–85% of their previously measured HRmax for 20–45 min per session, gradually progressing in intensity and duration until the end of the intervention
- Resistance exercise training - Participants performed up to 3 sets of 7 exercises on resistance machines for 6–15 repetitions of their maximum for 20–45 min per session (supplementary Tables S3, S41). Participants were recommended to rest for 1.5 to 2 min between sets. Intensity of resistance training gradually increased by increasing the load (weight) that adolescents were lifting for a fewer number of repetitions, targeting progressive improvements in muscular strength
- Combined aerobic and resistance exercise training - Participants performed both the Aerobic and the Resistance exercise training components during each exercise session
|Figure 1: Change in body weight and body fat (left axis) and reduction in energy intake (right axes | Alberga. 2017).|
Accordingly, it is not totally surprising that all groups lost weight and more importantly body fat (body composition was measured by a fancy MRI) over the course of the study.
|Figure 2: Changes in muscle mass and resting metabolic rate (Alberga. 2017).|
Do not jump to false black-and-white conclusions: I know, life would be easier if there were just black and white, but it would also be boring without "color" or, as in the case of the effects of lean mass on one's resting energy expenditure, the nuances of relevant vs. irrelevant lean mass gains. There's no doubt about it: Lean mass gains or losses of 10% of the total body weight will have significant beneficial/negative effects on your RMR (the overall effect will yet also depend on fat loss). If you scrutinize the data from the study at hand, the meager 900g of muscle and 1.8 kg of total lean mass the resistance training group added to their overweight frames amounts to only 1-2% of the subjects' total body mass. And still, the scientists are right, when they say that there's a "widespread misperception that resistance training increases RMR through its direct effect on increasing fat-free mass" (Alberga. 2017). It is, and this takes us back to where we have been coming from, more complex than that... but that's a topic for another SuppVersity article and another study with different subjects and greater increases in lean and decreases in fat mass.As the data from the meta-analysis by Schwartz et al. (Figure 3) shows, that is not really surprising. It is well established that weight loss - albeit in this case in adults and of (in almost all cases) significantly more body mass - will almost linearly reduce subjects' metabolic rate.
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