Despite mounting public health concerns about obesity and persistent social pressures dictating that slim is beautiful, young women in their '20s consistently exercise less than young men.
And young black women showed significant declines in exercise between 1984 and 2006, according to a University of Michigan study to be published in the October issue of the American Journal of Public Health.
The study is one of the first to analyze long-term patterns in weight-related activities, and to assess how these patterns vary by gender, race and ethnicity, and socioeconomic status.
The disparities in health behaviors the study reveals are consistent with disparities in the prevalence of obesity, particular among women, according to Philippa Clarke, lead author of the study and a researcher at the U-M Institute for Social Research (ISR).
The study is based on data obtained every two years from 17,314 men and women who were aged 19 to 26 between 1984 and 2006. The participants were part of a follow-up panel drawn from the Monitoring the Future Study, conducted by ISR. The analysis was funded by the Robert Wood Johnson Foundation, as part of the Youth, Education, and Society Project, also based at ISR.
For the study, the researchers looked at trends over a 23-year-period in six different health behaviors. They measured how often participants reported eating breakfast, and eating at least some green vegetables and fruit; how often they exercised vigorously (jogging, swimming, or calisthenics); how often they got at least seven hours of sleep, and how much television they watched on an average weekday.
"Agreement is growing that the source of the obesity epidemic lies in an environment that produces an energy gap, where energy intake exceeds energy expenditure even by as little as 100 excess calories per day," wrote Clarke and co-authors Patrick O'Malley, Lloyd Johnston, John Schulenberg and Paula Lantz, all researchers at ISR.
The finding that young women consistently exercised less than young men, suggests that differences in energy expenditure could play a role in gender disparities in obesity and overweight.
The frequency of eating fruit and vegetables remained relatively stable among young adult women but declined significantly among young men. Young men also reported eating breakfast less often than did young women.
Both men and women reported a steady decline in the frequency of getting at least seven hours of sleep each night.
Despite the focus on television viewing as an important determinant of obesity, the researchers found that the amount of time men and women spent watching TV stayed relatively stable.
When the researchers compared behaviors of different racial and ethnic groups, they found some major differences. For example, although white women showed a steady increase in the frequency of eating breakfast, the trajectory for non-Hispanic black women declined until 1996 and only began to increase in 2000.
Although fruit and vegetable consumption changed little among young adults, consumption of both was consistently lower among black and Hispanic men and women in any given year.
And although the frequency of exercise remained relatively stable among young adult women in general, among black women, the frequency of exercising steady declined.
In addition, black and Hispanic women showed greater declines than white women in the frequency of getting at least seven hours of sleep a night. They also were less likely than white women to report eating breakfast, and eating fruits and vegetables.
Among men, those from lower socioeconomic backgrounds reported dramatic declines in sleep, after adjusting for race and ethnicity.
Minority racial and ethnic groups, and women from lower socioeconomic groups, also reported watching television more often than whites and women from more affluent backgrounds.
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