Physical Activity in the Treatment of Obesity-related Health Risk: Is Weight Loss the Optimal Target?
However, as Dr. Ross and I have argued in a recently published paper in the Canadian Journal of Cardiology, several lines of evidence suggest that weight loss is not absolutely necessary to observe substantial health benefit from exercise. Thus, an apparent resistance to weight-loss should never be a reason for stopping an exercise program – read on to find out why.
First, it is well established that increasing physical activity and associated improvement in cardiorespiratory fitness are associated with profound reductions in coronary heart disease and related mortality independent of weight or BMI. Second, exercise (even a single session, as I had previously discussed) is associated with substantial reduction in several cardiometabolic risk factors (such as blood pressure, glucose tolerance, blood lipids, etc.) despite minimal or no change in body weight. Third, waist circumference and abdominal fat (arguably, the most dangerous fat) can be substantively reduced (10-20%) in response to exercise with minimal or no weight loss. In fact, significant reductions in fat mass often occur concurrent with equal increases in muscle mass in response to physical activity - equal but opposite (and beneficial!) changes which are not detected by alterations in body weight on the bathroom scale.
Indeed, as illustrated in a Figure taken from our recent publication, we propose three distinct scenarios for which an increase in physical activity is associated with substantial reduction in obesity related health risk with or without weight loss. That all three scenarios described are associated with attenuated CVD risk should be encouraging for both the patient and the clinician.
From Ross and Janiszewski, 2008. Benefits of increasing physical activity levels in obese individuals: 3 possible scenarios. Note the benefits in scenarios 2 and 3 where BMI or weight does not change. BMI – body mass index, WC – waist circumference, CRF – cardiorespiratory fitness.
In all, these observations bring to question whether weight loss is the optimal outcome for determining the efficacy of treatment strategies designed to reduce obesity related co-morbidities. We suggest that overweight/obese individuals and clinicians alike look beyond weight loss as the only indicator of treatment success when targeting obesity-related health risk. Remember that increasing physical activity levels will lead to substantial health benefits – even if the scale doesn’t budge.
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