Recent research from the Arnold School of Public Health at the University of South Carolina supports many scientists’ and practitioners’ long-held position that regular moderate-to-vigorous physical activity is associated with lower levels of adiposity (i.e., body fat). The study, published in Medicine & Science in Sports & Exercise, examined physical activity, diet quality and two measures of adiposity in a cross-sectional sample of nearly 5,000 men and women that is representative of the U.S. population. Led by professor, Dr. Russell Pate, department of exercise science, the team used data from the National Health and Nutrition Examination Survey to look at physical activity and diet quality in relation to body mass index and waist circumference across the adult lifespan.
Although 70 percent of Americans are considered overweight or obese, previous studies have not examined the associations between physical activity, diet quality, and measures of body fat in a representative sample of U.S. adults that included both genders and all age groups. In addition, no studies have examined changes in these factors across age groups, even though it is well known that Americans gain weight and body fat as they age.
In this new study, the Arnold School researchers found that, within all gender and age groups (which ranged from 20-29 to 70+), higher levels of moderate-to-vigorous physical activity were associated with lower levels of body mass index (BMI) and waist circumference. In contrast, higher diet quality was associated with lower BMI and waist circumference in only a few gender and age groups.
In addition, the researchers examined physical activity, diet quality, and the weight status variables across the age groups. Very consistently, with increasing age, physical activity decreased, diet quality increased, and BMI and waist circumference increased. These findings suggest that decreases in physical activity with age account for a significant portion of the increases in obesity that occur with increasing age. “When you look across all of the age and gender groups that we examined,” says Dr. Pate, “you see that even though diet quality goes up, weight status goes up as well; this correlation points to declining physical activity as the most significant factor in increasing weight trends.”
The research team recognizes the important role diet quality plays in weight status and overall health status. However, the increased adiposity measures/decreased physical activity (despite diet improvements) relationship revealed by this study indicates that physical activity’s role as an underlying factor in obesity has been undervalued.
“When looking at large, representative samples, individual eating habits don’t explain secular trends the way that physical activity has done in this study,” says Dr. Pate. “This study focuses more on a public health surveillance approach — rather than an emphasis on the individual.”
Still, individuals can benefit from the findings of this study. The researchers believe that these findings support the need for physicians, clinicians and public health educators to stress the importance of maintaining higher levels of physical activity over time. Specifically, Americans should aim to meet the federal physical activity guideline, 150 minutes of moderate intensity physical activity per week. “Once established, obesity is very challenging to treat, so prevention is key,” Dr. Pate says.
To further build on these findings, the team recommends that future research include longitudinal studies with excellent measures of physical activity and dietary intake, following individuals across the adult lifespan.
Co-authors on the study include Dr. Sharon Taverno Ross (University of Pittsburgh), Dr. Angela Liese (department of epidemiology and biostatistics) and Dr. Marsha Dowda (department of exercise science).