Tag Archives: exercise

Exercise for Weight Loss? Not Much Is Better Than Lots…

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Some additional research on the exercise front, this time out of the University of Copenhagen. In the paper, “Body fat loss and compensatory mechanisms in response to different doses of aerobic exercise–a randomized controlled trial in overweight sedentary males” (American Journal of Physiology), researchers assert that

Although well recognized as an important means for weight loss maintenance (9), the role of habitual endurance training in weight loss is scrutinized, and it has been suggested that exercise leads to compensatory responses. In the current study, we show that despite that one group undertook twice the amount of endurance training, the reduction in body weight and, more importantly, in body fat was the same as the weight loss and was equal among the two groups (a healthy weight loss). Surprisingly, the reduction with the moderate-dose exercise was far greater than what could be explained by the increased energy expenditure from the training itself (no compensation).

Again, the group that did 2x the amount of exercise wound up losing the same as the group that did less. But if you did nothing, you didn’t lose as much. Sound confusing? Gretchen Reynolds sums it up nicely in her New York Times article, “It found that exercise does seem to contribute to waist-tightening, provided that the amount of exercise is neither too little nor, more strikingly, too much.”

The researchers speculate that one of the reasons the people who exercised the most didn’t lose as much weight is that they tended to move less when not working out, as if they were fatigued…so over the course of the day, they burned fewer calories. This is oft speculated to be a reason for the exercise/weight loss paradox.

On a semi-related note, I’m working my way through Phinney and Volek’s, The Art And Science of Low Carbohydrate Performance again, and in that, they do a quick survey of the literature related to how exercise tends to REDUCE resting energy expenditure. In it, they write,

There are 4 well-controlled, inpatient, metabolic ward studies (the gold standard for human research) published from 1982 thru 1997 that showed statistically significant reductions in resting metabolic rate when overweight subjects performed 300-600 Calories per day of endurance exercise for weeks at a time[28-31]. There are no equally rigorous human studies showing the opposite. There are animal (rat) studies that show the opposite, and there are human studies done under less controlled conditions that show the opposite. However there are also similarly less rigorous studies that agree with the above four gold-standard studies. (39)

So is this a possible explanation for the results of the Copenhagen study? Perhaps. While the results are interesting, at the end of the day, it still does not appear that exercise is that much of a contributor to weight loss. While it does have an effect, I’ll still maintain that diet is the primary agent involved in shedding weight.

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Dieting vs. Exercise for Weight Loss: Recent Research Survey

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Gretchen Reynolds has a nice piece today on the diet vs. exercise schism that many of us come to terms with on our weight loss journeys. Citing two new pieces of research (one of which has already been covered here), she notes how research continues to suggest that exercise is a minor contributor to weight loss (compared to diet) and that the oft cited adage that that is frequently invoked to promote weight loss (“Exercise speeds up your metabolism which increases weight loss”) isn’t really all it’s cracked up to be when scrutinized:

One of the few studies ever to have scrupulously monitored exercise, food intake and metabolic rates found that volunteers’ basal metabolic rates dropped as they lost weight, even though they exercised every day. As a result, although they were burning up to 500 calories during an exercise session, their total daily caloric burn was lower than it would have been had their metabolism remained unchanged, and they lost less weight than had been expected.

So much for the increased metabolic effects of exercise… Looking forward to reading the actual studies referenced by Reynolds (currently only an abstract is publicly available for the second one).  Let’s see if these results from it can be reproduced.

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Research for Athletes: Going Low Carb Doesn’t Hurt Athletic Performance

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Recent research published in the Journal of the International Society of Sports Nutrition calls into question the notion that very low-carb ketogenic diets are unsuitable for athletes because they will not be able to achieve commensurate levels of performance without an adequate supply of glucose (derived from carbohydrate ingestion).

The researchers took 8 athletes, measured their performance in a variety of exercises while eating a standard Western diet, then they they put the athletes on a Very Low Carbohydrate Ketogenic Diet for thirty days and measured their performance on the same exercises. The result? Fascinating:

No significant differences were detected between VLCKD and WD in all strength tests. Significant differences were found in body weight and body composition: after VLCKD there was a decrease in body weight (from 69.6 +/- 7.3 Kg to 68.0 +/- 7.5 Kg) and fat mass (from 5.3 +/- 1.3 Kg to 3.4 +/- 0.8 Kg p < 0.001) with a non-significant increase in muscle mass.

That’s right, no detectable difference in performance. None. Nada. Zip. Oh yeah, the ketogenic low-carb dieters also lost fat while keeping muscle mass constant.

One obvious limitation to this study is that it appears to be focused on resistance exercise. I wonder what the results would be for runners… Thoughts?

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Do I Need to Exercise to Lose Weight?

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Research

Changes in Plasma Lipids and Lipoproteins in Overweight Men during Weight Loss through Dieting as Compared with Exercise – New England Journal of Medicine

As compared with controls (n = 42), dieters (n = 42) had significant loss of total body weight (-7.8±0.9 kg [mean ±SE]), fat weight (-5.6±0.8 kg), and lean (nonfat) weight (-2.1±0.5 kg) (P<0.001 for each variable), and exercisers (n = 47) had significant loss of total body weight (-4.6±0.8 kg) and fat weight (-3.8±0.7 kg) (P<0.001 for both variables) but not lean weight (-0.7±0.4 kg). Fat-weight loss did not differ significantly between dieters and exercisers. All subjects were discouraged from altering their diet composition; however, dieters and exercisers had slight reductions in the percentage of kilojoules derived from fat.

A meta-analysis of the past 25 years of weight loss research using diet, exercise or diet plus exercise intervention – International Journal of Obesity

The data shows, however, that a 15-week diet or diet plus exercise program, produces a weight loss of about 11 kg, with a 6.6(+/-0.5) and 8.6(+/- 0.8) kg maintained loss after one year, respectively.

Articles

Exercise and Fat/Weight Loss 1 – Lyle McDonald

But the simple fact is that, for the average untrained individual, realistic amounts of activity are unlikely to have massive direct impacts on either body weight or body fat; the caloric expenditure simply isn’t significant enough to impact on anything.  As well, changes in diet have the potential to make a much greater contribution to the creation of a caloric deficit; removing 500 or even 1000 calories per day from the diet can usually be achieved much more readily than adding the same amount of activity.  At least in certain populations.

Exercise and Fat/Weight Loss 2 – Lyle McDonald

Certainly larger amounts of exercise can approach significance (and as folks become fitter, they can burn more calories with activity) but the idea that a little bit of exercise is going to have a massive impact on anything is fairly misguided.