JUDITH WYLIE-ROSETT, EDD, RD FOR THE DIABETES PREVENTION PROGRAM RESEARCH GROUPOBJECTIVE -Diabetes Prevention Program (DPP) participants randomized to the intensive lifestyle intervention (ILS) had significantly reduced risk of diabetes compared with placebo participants. We explored the contribution of changes in weight, diet, and physical activity on the risk of developing diabetes among ILS participants.RESEARCH DESIGN AND METHODS -For this study, we analyzed one arm of a randomized trial using Cox proportional hazards regression over 3.2 years of follow-up.RESULTS -A total of 1,079 participants were aged 25-84 years (mean 50.6 years, BMI 33.9 kg/m 2 ). Weight loss was the dominant predictor of reduced diabetes incidence (hazard ratio per 5-kg weight loss 0.42 [95% CI 0.35-0.51]; P Ͻ 0.0001). For every kilogram of weight loss, there was a 16% reduction in risk, adjusted for changes in diet and activity. Lower percent of calories from fat and increased physical activity predicted weight loss. Increased physical activity was important to help sustain weight loss. Among 495 participants not meeting the weight loss goal at year 1, those who achieved the physical activity goal had 44% lower diabetes incidence.CONCLUSIONS -Interventions to reduce diabetes risk should primarily target weight reduction. Diabetes Care 29:2102-2107, 2006T he Diabetes Prevention Program (DPP) reported a 58% reduction in the incidence of diabetes over almost 3 years in subjects treated with an intensive lifestyle intervention (ILS) compared with participants treated with placebo (1). The ILS involved changes in diet and physical activity aimed at producing weight loss, but the study did not randomly assign each component of the intervention. However, there was variation in the change in diet, physical activity, and weight loss among ILS participants (2). Thus, we analyzed the relative contributions of changes in diet, physical activity, or weight loss to the reduction in diabetes incidence and assessed the contribution of diet and activity changes on weight loss. This report extends the understanding of how the ILS resulted in lower diabetes incidence (1) by assessing the impact of meeting intervention goals and on the changes in risk factors among individuals randomized to the ILS.RESEARCH DESIGN AND METHODS -The design, methods, recruitment, and characteristics of the DPP participants have been reported elsewhere (3,4). In summary, participants were aged Ն25 years, had a BMI of Ն24 kg/m 2 (Ն22 kg/m 2 in Asian Americans), and had impaired glucose tolerance during an oral glucose tolerance test, based on DPP criteria (5). Participants were excluded if they had diabetes or a number of other conditions or medications. All participants gave written informed consent after approval by the appropriate institutional review board. ILSThe ILS has been described (6). Goals were to reduce weight by 7% from baseline, to achieve and/or maintain at least 150 min per week of moderate physical activity, and to reduce total dietary fat to Ͻ25% of calorie...

The simple, short questionnaires on activity and inactivity used in the Nurses' Health Study II are reasonably valid measures for epidemiological research.

Substantial declines in physical activity occur during adolescence in girls and are greater in black girls than in white girls. Some determinants of this decline, such as higher body-mass index, pregnancy, and smoking, may be modifiable.

There was a need to design a questionnaire that could accurately assess the activity patterns of Native Americans to evaluate the relationship between physical activity and diabetes. Such a questionnaire was developed and implemented into the data collection scheme of the prospective Pima Indian Study of Arizona. The questionnaire, which assesses historical, past-year, and past-week leisure and occupational activity, was examined in 29 Pima individuals aged 21-36 yr and was shown to be reliable with test-retest correlations (rank-order correlations ranged from 0.62 to 0.96 for leisure and occupational activity). Reproducibility of the past-year leisure physical-activity estimate was determined in 69 participants aged 10-59 yr and was found to be reliable in all age-groups with the exception of the 10- to 14-yr-old age-group (rank-order correlations were 0.31 in the 10- to 14-yr-old age-group compared to 0.88 to 0.92 in those greater than 20 yr of age). Validity of the current-activity section of the questionnaire was demonstrated indirectly through comparisons with activity monitors. The past-week leisure-activity estimate was related to the Caltrac activity monitor counts per hour (rho = 0.62, P less than 0.05, n = 17). In summary, a physical-activity questionnaire has been developed that is both reliable and feasible to use in the Pima Indian population to evaluate the relationship of physical activity to non-insulin-dependent diabetes mellitus.