The major finding of this study was that a lifestyle-based weight loss plus exercise intervention produced significant weight loss and improved physical function in obese, older women with mild to moderate physical impairments. Participants in the intervention group lost approximately 6% of their initial body weight and significantly improved physical function as measured by changes in gait, balance, transfers, and walking speed. In line with previous studies,21
participants in the educational control group also significantly improved their physical function, as measured by performance on the SPPB; the observed improvements on the SPPB in the Educational Control group may have been related to practice effects. Therefore, the difference in the improvement in scores between the two groups may represent the additive benefit of a lifestyle-based weight loss intervention. Muscle strength was also maintained in both the intervention and control groups.
Older adults may be particularly susceptible to the adverse effects of excessive body weight on physical function because of the decrease in muscle mass and strength that occurs with aging.22
A significant concern about encouraging weight loss in this population is that it could have a detrimental impact on muscle function and strength. We did not observe adverse effects on muscle function in the present study, as muscle strength was maintained among participants in the intervention group. Because participants in the intervention group maintained strength despite losing a significant amount of weight, this suggests that muscle quality (ie, strength/muscle volume) may have improved. Therefore, the findings of the present study are encouraging regarding the potential of lifestyle interventions to delay or prevent the development of disability in obese, older women. These findings are similar to one previous clinical trial that found that a lifestyle-based diet plus exercise intervention was effective in improving physical function in frail, obese, older adults.12
Given the disproportionately higher rates of obesity (>50%) and obesity-related comorbidities in African American women,1
interventions are urgently needed that can effectively reduce body weight and improve physical function levels in this high-risk population. To our knowledge, this is the first study to examine the effects of a lifestyle-based weight loss plus exercise intervention in obese, older African American women. In contrast to previous studies in younger and middle-aged African American women,23
we found that obese, older, African American women responded in a similar manner as obese, older, Caucasian women in terms of weight loss and improvements in physical function. The specific reason(s) for the divergence in findings from previous studies is unclear, but a number of factors may have influenced the effectiveness of our intervention in African American women, including the intervention setting (ie, church facilities), inclusion of a structured group-based exercise program, and a tailored dietary intervention approach, as well as participant characteristics (ie, age, motivation, health risk). Interestingly, among African American women who do achieve and sustain weight loss, significant improvements in cardiovascular disease risk factors have been observed,25
suggesting that weight loss may be effective in reducing the risk of chronic disease in this high-risk population.
The results of the present study should be interpreted in the context of its limitations. First, the sample size was relatively small, and the study was not adequately powered to detect differences between African American and Caucasian women in response to the intervention. Second, we did not directly measure body composition and therefore were unable to determine the proportion of fat versus fat-free weight lost. Third, participants completed just over two-thirds of the center-based exercise sessions (mean attendance = 70%). Although this exercise completion was lower than was anticipated, it is in line with previous studies that have found that participants complete approximately two-thirds of exercise prescribed, regardless of frequency recommended.11
The reasons for the lower than anticipated rates of attendance at exercise sessions were varied. Some participants reported being unable to attend exercise sessions due to changes in their schedule, and others reported preferring to exercise at home. Fourth, this study informs only about the effects of a short-term (ie, 6-month) weight loss intervention, which is not of sufficient duration to determine whether weight loss is sustained. An additional limitation of this study is that the participants were generally healthy, older adults; therefore, these findings may not be generalizable to older adults with more severe health conditions or functional limitations.
The present study also had a number of strengths. Few studies have tested the effects of a comprehensive lifestyle-based weight loss intervention in an older adult population with impaired physical functioning. Given that participants had a mean age of 68 years, this study provides preliminary information regarding how adults over the age of 65 years may respond to a comprehensive weight loss plus exercise program. In addition, the patient-centered outcomes (ie, walking speed, strength, and SPPB) used in this study have high relevance to older adults and have been found to predict disability, falls, institutionalization, and mortality. Another strength of this study is the inclusion of equal numbers of African American and Caucasian obese women. Additionally, all exercise sessions were conducted under direct supervision to ensure that participants exercised at the appropriate intensity and used proper exercise techniques. Finally, the intervention was carried out in a community setting and thus represents a unique approach to implementing lifestyle-based interventions within communities.