Few studies have tried to identify the factors that place middle-aged adults at risk for gaining weight, and the evidence that regular physical activity prevents weight gain is inconsistent. Two recent studies led by Northwestern University researchers Xiaoxing Z. He, M.D., M.P.H., and David W. Baker, M.D., M.P.H., examined weight gain among U.S. adults aged 51 to 61 years and the relationship of weight and physical activity to overall health and functioning. The studies were supported by the Agency for Healthcare Research and Quality (HS10283). The studies are summarized here.
He, X.Z. and Baker, D.W. (2004). "Changes in weight among a nationally representative cohort of adults aged 51 to 61, 1992-2000." American Journal of Preventive Medicine 27(1), pp. 8-15.
In this study, both men and women aged 51 to 61 in all ethnic groups gained weight from 1992 to 2000, and their current levels of physical activity did not appear to protect against weight gain. The researchers analyzed activity level and changes in weight and body mass index (BMI) of 7,391 ethnically diverse community-dwelling U.S. adults aged 51 to 61 using data from the 1992, 1994, 1996, 1998, and 2000 Health and Retirement Survey interviews. The baseline interview (1992) asked respondents how often they participated in light physical activity, such as walking, dancing, and gardening; vigorous exercise or sports such as running, swimming, bicycling, or heavy housework; and work-related physical activity such as lifting heavy loads.
The mean weight gain during the study period was higher for women (3.67 pounds) than for men (3.15 pounds). White men and women had the lowest baseline BMI, but tended to gain more weight than other racial/ethnic groups. After controlling for other factors, individuals who were older or had higher baseline weight showed less weight gain. Men who reported poor health at baseline were less likely to gain weight than men who reported excellent health. Race, education, and income were not associated with weight gain, after accounting for other factors.
Regular light or vigorous recreational activities, household chores, or work-related activities were not associated with less weight gain. The authors conclude that high-frequency, moderate-intensity exercise is probably needed for weight loss. They suggest that physicians, nurses, and public health messages focus less on the benefits of exercise for weight control and instead emphasize the other health benefits that accrue from regular exercise.
He, X.Z. and Baker, D.W. (2004, September). "Body mass index, physical activity, and the risk of decline in overall health and physical functioning in late middle age." American Journal of Public Health 94(9), pp. 1567-1573.
Although maintaining ideal body weight is important in preventing decline in overall health and physical functioning, regular exercise can reduce the risk of health decline even among individuals who cannot achieve ideal weight, according to this study. The investigators used data from the 1992, 1994, and 1996 Health and Retirement Survey to examine the relationship between BMI, exercise, overall health, and physical functioning among 7,867 adults who were aged 51 to 61 years during the study period.
After adjustment for risks of health decline and new physical problems, overweight and obese individuals had a 29 percent and 36 percent, respectively, higher risk of health decline and a 27 percent and 45 percent, respectively, higher risk of developing a new physical difficulty (for example, being unable to walk as far or climb a flight of stairs without resting). The good news is that regular exercise significantly reduced the risk of health decline and development of a new physical difficulty, even among obese individuals.
For example, after adjusting for other factors, the relative risk of a decline in overall health was over 30 percent lower for individuals who performed light exercise one to three times per month, one to two times per week, or three or more times per week, and 25 percent lower for individuals who ever performed vigorous exercise, whether they performed it an average of three or more times per week or less than once per month. Similarly, the risk of developing a new physical difficulty was 22 to 31 percent lower for individuals who performed light exercise more than once per month. This risk also declined 17 percent for those who performed vigorous activities less than once per month to as much as 43 percent lower for those who performed vigorous activities three or more times per week.
Editor's Note: According to another AHRQ-supported study on a related topic, strategies that increase the likelihood of patients identifying weight as a problem or that provide clinicians with a way to "medicalize" the patient's obesity are likely to increase the frequency of weight loss counseling in primary care visits. For more details, see Scott, J.G., Cohen, D., DiCicco-Bloom, B., and others (2004). "Speaking of weight: How patients and primary care clinicians initiate weight loss counseling." (AHRQ grants HS08776 and HS09788). Preventive Medicine 38, pp. 819-827.
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