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.
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