Healthy weight loss is one of the best ways that overweight adults can reduce their risk for cardiovascular disease and other illness. Many factors influence our ability to lose weight, such as psychological influences, social resources, and neighborhood influences, and our genes. A group of researchers in North Carolina hypothesized that one such psychological influence, one that can be affected through health interventions, is sense of self-efficacy about weight control (the belief that one is able to control one’s weight). The researchers’ article shows how this sense of efficacy was enhanced among older adults by a combined weight-loss and physical activity treatment.
The study was a randomized control trial that grouped older adults into three different treatments: a purely educational “Successful Aging” group, a physical activity group, and a group that combined a dietary and educational weight-loss program with physical activity. The researchers hypothesized that the combined group would be most effective, and that the success of this group would be affected by its ability to foster weight loss self-efficacy. Each group had a six-month intensive phase, followed by a 12-month maintenance phase that included one telephone and one in-person contact per month.
The physical activity and combined groups included organized exercise sessions during the intensive phase, with regular physical activity being encouraged during the maintenance phase. The weight-loss program, given only to the combined treatment group, included a personalized calorie-counting and food choice program and a diet-tracking book, which was reviewed weekly by program staff. Each group had their weight tracked and was given the Weight Efficacy Lifestyle questionnaire (WEL) to track weight loss self-efficacy. There were no significant demographic or health differences between the three treatment groups, and each group had similar rates of attendance.
The hypotheses about the effectiveness of the groups and the influence of self-efficacy on weight loss were both supported. The combined group had an average weight loss of 8.6% of body weight at the end of the six-month intensive phase, significantly more than in the other two groups, which averaged about 1% body weight loss. Levels of physical activity were significantly increased in the physical activity and combined groups, and not in the successful aging group. Further, statistical analysis showed that the effects of the intervention were partly mediated by changes in WEL scores, which also correlated with the number of days that individuals met their dietary goals.
The authors acknowledge some limitations to their study and to the use of the WEL questionnaire. For example, trait-based questionnaires like the WEL are not always effective at predicting how individuals will act in different contexts, particularly around issues such as weight-loss behavior that can be strongly influenced by fluctuations in environment and mood. This study, however, does manage to show a chain of influence between combined weight loss/physical activity interventions, weight-loss self-efficacy, and weight loss.
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