In a paper presented at the European Congress on Obesity last month, researchers concluded that weight gain in the United States over the past 30 years can be attributed almost entirely to calorie intake, as opposed to lack of physical activity. Scientists looked at data from previous large food and activity surveys and concluded that physical activity has changed little in recent decades whereas calorie intake has increased significantly, accounting for virtually all the observed weight gain. A related paper appears in this month’s American Journal of Clinical Nutrition.
Swinburn BA, Sacks G, Ravussin E. Increased energy intake alone virtually explains all the increase in body weight in the United States from the 1970s to the 2000s. Report presented at: European Congress on Obesity; May 8, 2009. Obesity Facts. 2009; 2(Suppl 2):6.
Swinburn BA, Sacks G, Lo SK, et al. Estimating the changes in energy flux that characterize the rise in obesity prevalence. Am J Clin Nutr. 2009;89:1723-1728.
I have long felt that poor eating habits are much more of a public health problem than lack of exercise. That is not to say that being sedentary is not a problem. But, if you look at the two issues side-by-side, as the above research concludes, our society's intake of calories has increased substantially in recent decades, while our energy expenditure has remained fairly stable. Most preventive medicine health experts that I follow, advocate a major change in eating style and 'moderate' exercise. American problems (and increasingly health problems around the world) are largely linked to huge increases in the amount of fat, sugar and salt we consume. Cheap low nutrition, high fat/salt/sugar food is abundantly available whether you are rich or poor. The obesity problem does not appear to discriminate -- low income, middle income, high income, young, old, etc. are all becoming more obese.
I notice that a lot of people focus on increasing their exercise when they have a weight or health problem. That is good, but if diet is neglected, the results will often be minimal. When individuals reach the stage where they are very motivated to reduce their weight and improve their health (often after a health scare), they opt towards increasing their exercise and making few if any real changes in their eating style. Exercise is apparently the 'lessor of the two evils.' But I have observed that those that reduce their weight and keep it off, and make substantial gains in their health focus on diet primarily and secondarily (and still importantly) on increasing their level of activity.