Thursday, July 28, 2011

Aerobic Exercise Alone Does Not Lead to Weight Loss

Readers will recall my recent post on the notion that the weight-loss that occurs in some people with exercise is probably related more to the impact that exercise has on caloric intake than on the actual amount of calories burnt.

It is therefore not all that surprising, that a systematic review and meta-analysis of the literature on the impact of isolated aerobic exercise on body weight, by Adrian Thorogood and colleagues from Montreal and Quebec, published in the latest issue of the American Journal of Medicine, shows rather limited impact of this intervention on body weight.

In their study, the researchers, searched for all published randomized controlled trial reports of aerobic exercise through January 20, 2010 and identified 14 trials involving 1847 overweight and/or obese patients.

While six-month programs were associated with about 1.6 Kg reduction in weight and about 2 cms reduction in waist circumference, twelve-month programs did not lead to any additional weight loss.

As the authors note:

“Previous systematic reviews suggest a linear dose-response relationship between aerobic exercise and weight loss, but only for interventions <16 weeks in duration with a controlled diet. This relationship has not been shown for longer interventions.

These findings have some important clinical implications.

1) When indicated(!), taking up an aerobic exercise program alone (i.e. without also changing your diet), is not the most effective way to achieve even a modest 5% weight loss.

2) The study also shows that maximum weight loss with this intervention is probably achieved after about six months, whereafter, continued exercise helps maintain weight loss, but does not reduce weight further.

Of course, none of this should be taken as an excuse to abandon or not include a healthy bout of aerobic activity into your daily routine. However, if your only goal is to lose weight (which, by the way, it should not be), you are likely to be disappointed.

Indeed, there is ample data showing that including regular exercise into your routine increases your chances of maintaining weight stability and avoiding weight regain.

And of course, there are countless benefits of exercise, that cannot be measured on a scale.

In the end, weight loss requires reducing and restricting caloric intake – the idea that you can ‘burn’ enough calories through exercise to lose and significant amounts of weight is nonsense – alas, a myth that sells gym memberships and keeps hosts of weight-loss TV shows in business.

Finally, let’s always remember that neither diet nor exercise alone should ever be seen as a treatment for obesity, at least not without first conducting a careful evaluation of the potential causes and consequences of excess weight and carefully weighing the pros and cons of any weight-loss recommendations.

AMS
Cambridge, UK

Thorogood A, Mottillo S, Shimony A, Filion KB, Joseph L, Genest J, Pilote L, Poirier P, Schiffrin EL, & Eisenberg MJ (2011). Isolated aerobic exercise and weight loss: a systematic review and meta-analysis of randomized controlled trials. The American journal of medicine, 124 (8), 747-55 PMID: 21787904

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4 Responses to “Aerobic Exercise Alone Does Not Lead to Weight Loss”

  1. fredt says:

    So what is a person to do? Non conventional advise for weight loss is to do resistance training.

    Exercise during weight loss is critical to prevent muscle catabolism, that is the use of our own muscles for energy. This is a real occurring physiological process, and is destructive. Resistance training of some type is most suitable. Machines are the safest for obese and grossly obese. Take ever muscle to “failure” once per week at no more than 75% of your maximum strength. Resistance training stimulates anabolism, which will help with weight control, once the excess weight is reduced. Tabata, high intensity, SS, and similar forms have similar effect. More information can be found at http://www.bodybyscience.net.

    The amount of calories used is the sum of basic metabolism plus exercise. Unless the exercise is long duration, the total energy does not amount to much, and exercise will make us hungry, so we eat more. Intake must also be controlled, which is easier for me on low carb program. No sugar, grain, or omega 6 oils.

  2. Alana says:

    I’m curious about bullet (2) above. Why was “maximum weight loss” achieved after six months? How much weight did the participants have to lose? If it was something like 30 pounds, this makes sense–but if it was something like 100–then I wonder why there was no further loss. Do you have any thought on why individuals would not lose any more weight from the seventh month to the 12th? Thanks.

  3. DeeLeigh says:

    Thanks for noting that being active is healthy and worthwhile even though it doesn’t necessarily lead to weight loss. In my opinion, being strong and active is absolutely the best way to be fat and healthy. One of the most problematic effects of yo-yo dieting is how it raises body fat percentage with regain, making large people feel weak and overloaded rather than strong and capable.

    I’m not saying that people should aim to look like body builders. However, strength training, pilates, yoga and even basic calisthenics give us the strength we need to carry ourselves with grace. (and to prevent falls!) Regular aerobic exercise prevents problems with huffing and puffing, strengthen our hearts and lungs, and improves mood. Hell, even regularly climbing stairs and taking walks – especially if it’s done with good posture and a slightly challenging pace – prevents us from becoming embarrassingly out of shape.

    Who cares whether or not physical activity causes weight loss? It’s absolutely vital to quality of life, whatever your size.

  4. Steve Parker, M.D. says:

    Ever seen the TV show “Biggest Loser”? The contestants exercise like crazy but also drastically reduce caloric consumption. They lose dramatic amounts of weight, at least short-term.

    Would they lose as much weight if they simply cut back on calories? I doubt it. But the study at hand implies they would.

    (I’ve only seen the show once or twice and don’t remember whether the exercise was mostly strength training or aerobic. Probably a combination. I realize that replication of the Biggest Loser program for the average viewer at home is impossible.)

    I think the prize for the U.S. Biggest Loser is $250,000 (USD). That’s quite a motivator! Not to mention the 15 minutes of fame.

    -Steve

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