September 1, 2013
John DiTraglia MD
Last weekend I did the Chicago Triathlon - very slowly. The Chicago Triathlon has grown from 760 triathletes in 1983 to over 8,700 today. In 2006, the Chicago Triathlon was named the “World’s Largest Triathlon” by the Guinness Book of World Records for most participants in an International Distance. It seems that there are more and more of these kinds of events and there are more and more people doing them.
By my count Portsmouth has 10 a year - Two Big Bear Runs, Run for Your Life, TOSRV… Then why do we keep getting fatter? Readers of this column know that exercise, while wonderful for your health, is of no value in losing weight. Everyone used to think that exercise was important for losing weight but even the exercise gurus now admit that’s not true. Likewise exercise will not help you maintain or control your weight (whatever that means). Exercise for weight loss maintenance is the new mantra of many of those exercise pundits but it’s not true that exercise helps you maintain weight loss.
In an epidemiological study of this question (1) it was found that there was an increase in the prevalence of physical activity from 2001 to 2009 that was matched by an increase in obesity in almost all counties in the U.S. during the same time period. But if you controlled for indexes of poverty, unemployment, number of doctors, percent rural and baseline levels of obesity, then for every 1 percentage point increase in physical activity prevalence, obesity prevalence was 0.11 percentage points lower. All of those factors are associated with obesity, although, except for baseline obesity, I’m not sure why. But that’s still not much benefit to weight loss by exercise. These authors conclude that although the rise in physical activity levels will have a positive impact on the health of Americans by reducing cardiovascular diseases and diabetes, “other changes such as reduction in caloric intake are likely needed to curb the obesity epidemic.”
Dwyer-Lindgren L et al. Prevalence of physical activity and obesity in US counties, 2001—2011:a road may for action. Popul Health Metr. 2013 Jul 10;11(1):7