Run for your life
Dale M. Atrens
As both No. 10 and the popular press remind us on a daily basis, we are becoming fatter at an alarming rate. According to current projections by next Christmas most of us will show up in aerial photographs. An Australian newspaper warned that obesity was increasing so fast that today's parents will outlive their children. This suggests a lifespan reduction of more than 25 years in a single generation. We are told that the key to avoiding this grizzly fate is to become more active.
Although health authorities are loath to admit it, the sky may not be falling. Their recalcitrance on this essential point may stem from the fact that stable skies are bad for business. There's nothing like a riveting health scare to keep the cash registers jingling. During the great leap forward of corpulence longevity has increased greatly. It is absurd to expect this salutary trend to stop in its tracks and suddenly drag us into an abyss.
As usual, gluttony is said to be a major factor in the doom bearing down upon us. In spite of the chorus of calls for the head of Ronald McDonald, the clamouring is unjustified. Overeating is not the root of our current woes. As we've been getting fatter, caloric intake and fat intake have been declining. Far from sliding into gluttony most foul, we are becoming more abstemious.
There is surprisingly little evidence to indict sloth in the epidemic of obesity. Some studies find that active people are thinner, many find they're not. Equally important, most of the 'positive' studies can be interpreted as showing that fatness causes lack of exercise. If you've ever seen a fat person pole vaulting, this requires no further explanation. Further complications are added by the fact that sometimes an effect is found only in one sex or age group. The chaos is compounded by different effects in various nationalities.
In most countries physical activity is either static or increasing whereas obesity is increasing almost everywhere. Significantly, the United States tops both the physical activity and obesity tables. This certainly isn't a tribute to the slenderizing effects of physical activity. Portugal is at the bottom of the physical activity table and near the top of the obesity table. If you revile sloth cite Portugal; if you find indolence more congenial cite the USA. More broadly, such divergent results suggest that there is little relationship between sloth and obesity.
The Japanese are, as always, instructive. For several decades Japanese fat intake has been skyrocketing while their participation in exercise is largely restricted to watching sports on television. Their favourite exercise is Tai Chi, which is about as strenuous as yawning. In terms of both food intake and physical activity they are the polar opposites of the USA. The price they pay for their dissolute lifestyle? Their rate of obesity is one tenth that of the USA and they lead the world in longevity. Of course exercise is only one aspect of physical activity. A large amount of our total energy is used in commonplace activities. Authorities maintain that we are getting fatter because we no longer chop wood or get up to change channels on the television. The television remote control has become a symbol of the decadence of Western civilization. So far the chain saw appears to have escaped criticism. Labour saving gadgets are killing us — worse, they're making us fat.
The Cooper Institute of Aerobics Research helpfully suggests that we walk every supermarket aisle, whether we need to or not. This will doubtless turn the tide. The American Centers for Disease Control and Prevention urge us to walk 10,000 steps (about 5 miles) per day. A nutritionist with a particularly punitive bent suggests we strap pedometers on kids and not let them go to bed until they've clocked up 10,000. Imagine Big Brother in a jockstrap wielding a cattle prod.
Most people are incredulous when told that clinical studies provide no evidence that exercise promotes weight loss either with or without dieting. The exercise industry has yet to inform the public of this rather important caveat. Of course, letting this simple truth out of the bag would be very bad for business. In the area of public health the 'truth' is highly negotiable. Much of what the public has come to believe is marketing, not science. Health edicts based on cherrypicking the evidence have become the unfortunate norm.
In theory, exercise should promote weight loss, so why doesn't the theory work in the real world? One reason is that fat is such a good source of energy. One kg of fat provides enough energy to keep us going for about four days even if we eat nothing. Expressed another way, one kg of fat is the energy equivalent of walking 80 miles. If you are a brisk walker, that could take as little as 16 hours. In this light, the effect of the extra supermarket aisles urged on us by the Cooper Institute could well amount to several grams of fat over a lifetime.
Any increase in energy expenditure not compensated for by increased energy intake must cause weight loss. This is simple physics. However, mountains of data show that in the long run, exceedingly few can increase their energy expenditure enough to make a difference to their weight. Like it or not, the facts speak for themselves. To hector entire populations about what is at most a highly equivocal lifestyle deficiency has considerable potential for harm. Such an assault on the simple joys of leisure can only increase feelings of helplessness and self-loathing. Exercise may well have other benefits, but its impact on weight loss is negligible. It is not the moral or health imperative that its advocates make it out to be. The strident advocacy of 'run for your life' is yet another instance of pseudo-scientific tinkering with the lifestyles of entire nations.
30 January 2004
Dale M. Atrens, Ph.D. is Reader Emeritus in Psychobiology at the University of Sydney and Research Scholar at the River Centre Clinic, Sylvania, Ohio.
References:
J. J. Varo et al. Distribution and determinants of sedentary lifestyles in the European Union. International Journal of Epidemiology 32 (1):138-146, 2003.
J. Ribeiro et al. Overweight and obesity in children and adolescents: relationship with blood pressure, and physical activity. Annals of Human Biology 30 (2):203-213, 2003.
J. Stevens and E. M. Nowicki. Body mass index and mortality in Asian populations: implications for obesity cut-points. Nutrition Reviews 61 (3):104-107, 2003.
D. M. Atrens. The Power of Pleasure. Sydney: Duffy & Snellgrove, 2000.
W. C. Miller. How effective are traditional dietary and exercise interventions for weight loss? Medicine and Science in Sports and Exercise 31 (8):1129-1134, 1999.