Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults

Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults.

This study popped up on the social media yesterday and it’s caused quite an uproar among the pro-lifting crowd, mainly thanks to the last lines of the abstract which seem to say that “cardio is better than lifting weights”.

I don’t want to get into a full dissection of this paper, because I think, like most media-driven study-hysteria, it’s importance is overblown. I’d like instead to go over some thoughts that occurred to me as I read through the findings which might help slot these findings into a pragmatic framework.

  • I’ve had prior experience, both directly and in advising others dealing with “stuck” clients, with overweight and obese people not responding to the prescription of “just lift and watch your diet”. You can conjure up your own Pubmed explanations for why this might be, but the reality of it is that some folks just don’t respond well to that plan, and I don’t believe it’s because they are “really” just eating too much.
  • What has, however, worked consistently is taking these people away from an exclusive emphasis on lifting (and intense interval cardio) and getting them to do add light to moderate aerobic cardio. Even a half-hour to an hour of aerobic cardio, something as simple as a walk (my rule is “do something that makes you breathe hard”), can make all the difference, and suddenly the fat starts to come off.
  • Despite the internet trope to the contrary, I have known even “normal weight” (meaning normal body comp) people who see no substantial visual changes from lifting weights alone. Yes, they develop more muscle and drop body fat (by percentage), but the way those changes distribute just creates a “does this guy even lift?” effect. Underweight people (“ectomorphs”) of either gender will naturally tend to “shape up” via lifting, as will pudgy people who might otherwise be naturally lean outside an environment encouraging overeating. People who seem to have a genuine biological tendency to be heavier and “thicker” (“endomorphs”) don’t always seem to get this benefit, and they really seem to need aerobic cardio along with diet and lifting to see the best effect.
  • Most of these people have been women out of their early twenties. Whether this applies across the board or is an artifact of my own construction I leave to the reader, but I do believe there may be some genuine metabolic reasons behind this. It wouldn’t surprise me to find that this can apply to people of any age or gender, though, as my experience need not be representative of the statistical reality. The point is having the strategy when you run into the roadblock.

What this paper found doesn’t conflict with these observations.

The two modes of exercise consistently differed in their effects on body composition. Body weight and fat mass significantly decreased in both AT and AT/RT but not in RT, suggesting that aerobic exercise is more effective in changing these measures. However, the change in lean body mass in both RT and AT/RT was significantly greater than that in AT, a finding supported by similar observations for the measure of thigh muscle area. Having the benefit of both modes of exercise allowed AT/RT to decrease body fat percent significantly more than either AT or RT, due to decreased fat mass combined with increased lean body mass. Similarly, there was an apparent additive effect of the two modes of exercise on waist circumference, as AT/RT significantly decreased waist circumference more than AT or RT.

I have some questions about their methods for assessing calorie intake, but for the moment let’s just assume that their report of intake as being more or less equivalent between the three groups is right.

You could then say “Well with a tighter diet these folks would lean out by just lifting weights.” Let’s grant that this is true, although it need not be. Even so, there are people, and I include myself among them, who’d rather have the food and spend the time training harder. This need not even be a physiological effect, but rather an effect of “living what you want to be”, so to speak, and that’s a factor I’ve come to believe is far more important than any reductive measure of ‘efficiency’.

As I’m reading this, that strategy is validated: “there was an apparent additive effect of the two modes of exercise on waist circumference, as AT/RT significantly decreased waist circumference more than AT or RT.”

That may not seem like much, but I think that this sentence, when taken with the finding of increased LBM and reduced fat mass, is the real clincher. Even though, strictly speaking, there may be no superiority to the combined modes of exercise in terms of absolute fat loss or weight loss, that’s beside the point.

The authors reach that conclusion based on ‘time-efficiency’ and an assumption that it is the absolute reduction in fat mass that is definitive of health. While I can admit (grudgingly) that the former will be a factor of importance to some people, I can’t entirely accept the latter. Amounts of fat mass are certainly important, but if we’re going to talk of health then we can’t really leave out the importance of LBM, the distribution of fat mass relative to LBM (which, as measured by waist circumference, we saw improved in an ‘additive effect’ by the combined modes of training), and the myriad positive effects of placing the body under regular loading.

I don’t entirely agree with the author’s conclusions, but the study itself is interesting and I believe that, if anything, it suggests that those looking to reduce fat mass and improve the distribution of lean and fat mass should be lifting and keeping some conditioning work in the mix.

Written by Matt

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