A new study reveals that physical activity is more likely to positively effect obesity than diet. This is based on the fact that the calorie consumption of Americans has remained steady over the last 20 years while the amount of time being sedentary has increased dramatically.
The draft study from the Stanford University School of Medicine looked at 22 years of national health survey results, from 1988 to 2010. During those years, the percentage of women reporting “no physical activity” jumped from 19 percent to 52 percent while the percentage of men rose from 11 percent to 43 percent. Concurrently, obesity also rose, climbing from 25 to 35 percent in women and from 20 to 35 percent in men. Significantly however, the number of calories consumed each day barely changed.
The proportion of processed versus raw foods was not part of the examination. The study was observational, meaning that it recognized a correlational link between weight gain and sedentary lifestyles.
Exercise and diet are both known to contribute to obesity, but this study helps determine which is most important for Americans seeking to make wise decisions. Obesity is known to contribute to cardiovascular disease, cancer, and other well-documented conditions, including increased mortality. From 1960 to 2002, the average weight for men aged 20 – 74 rose from 166 pounds to 191 pounds (15 percent). During the same period, the average weight for women of the same age went up from 140 pounds to 164 pounds (17 percent). In 2010, one in three American adults were considered obese by the U.S. Government.
Although the data did not show a sizable increase in the calories consumed during the 20 year study period, it nevertheless referenced a sizable increase from earlier periods: Americans today consume 500 calories more per day than they did in the 1970s and 800 calories more than in the 1950s. When reporting underestimations are taken into account, Americans now consume 2,200 to 3,300 calories each day on average.
The lead author, Uri Ladabaum, an associate professor of gastroenterology, described the drop in leisure-time physical activity as “dramatic.” Although actual cause and effect conclusions cannot be drawn from the examination, Ladabaum is nevertheless clear that exercise and physical activity are important determinants of the obesity trend. His study found “a significant association” between the level of leisure-time physical activity and Body Mass Index and girth, or waist circumference.
Based on their findings, Ladabaum’s team identified the ideal amount of moderate exercise as more than 150 minutes per week. Alternately, vigorous exercise should ideally be for a minimum of 75 minutes per week.
Data used in the study came from a long-term project sponsored by the Centers for Disease Control and Prevention (CDC) called the National Health and Nutrition Examination Survey. The annual sampling assembles information from a number of surveys and physical examinations in an attempt to assess Americans’ health. Participants recorded the intensity, duration and frequency of the exercise they engaged in within the previous month.
The final study will appear in The American Journal of Medicine in August. Pamela Powers Hannley, a public health doctor and managing editor of the journal, cautioned against over-simplifying the matter of obesity, saying that is a complex issue with roots throughout society. As an example, she wrote of the daily struggle single mothers live, balancing work and child care. “They may lack the time or resources to exercise. We shouldn’t assume that people are just lazy.”
Recommendations to control obesity with specific diet or exercise suggestions, though important, are not enough, she said. “It’s going to take widespread change … We need to work with communities, employers and local governments to enable healthy lifestyles by ensuring that there are safe spaces to exercise that are cheap or free.”
By Gregory Baskin