Quasi-causal associations of physical activity and neighborhood walkability with body mass index: a twin study.

OBJECTIVE: Physical activity, neighborhood walkability, and body mass index (BMI, kg/m(2)) associations were tested using quasi-experimental twin methods. We hypothesized that physical activity and walkability were independently associated with BMI within twin pairs, controlling for genetic and environmental background shared between them. METHODS: Data were from 6376 (64% female; 58% identical) same-sex pairs, University of Washington Twin Registry, 2008-2013. Neighborhood walking, moderate-to-vigorous physical activity (MVPA), and BMI were self-reported. Residential address was used to calculate walkability. Phenotypic (non-genetically informed) and biometric (genetically informed) regression was employed, controlling for age, sex, and race. RESULTS: Walking and MVPA were associated with BMI in phenotypic analyses; associations were attenuated but significant in biometric analyses (Ps<0.05). Walkability was not associated with BMI, however, was associated with walking (but not MVPA) in both phenotypic and biometric analyses (Ps<0.05), with no attenuation accounting for shared genetic and environmental background. CONCLUSIONS: The association between activity and BMI is largely due to shared genetic and environmental factors, but a significant causal relationship remains accounting for shared background. Although walkability is not associated with BMI, it is associated with neighborhood walking (but not MVPA) accounting for shared background, suggesting a causal relationship between them.

Increases in physical activity may affect quality of life differently in men and women: the PACE project.

PURPOSE: Obesity is associated with impaired quality of life (QoL), but less is known about physical activity. We investigated how decreases in body mass index (BMI) and increases in activity affect obesity-specific QoL and potential gender differences in associations. METHODS: In a large worksite randomized trial of a multilevel intervention on diet and physical activity behaviors, we conducted a cohort analysis at two years of follow-up. Self-reported activity and Obesity and Weight Loss Quality of Life (OWLQOL) were analyzed for individual-level associations using linear mixed models accounting for random worksite effects. RESULTS: Gender modified the BMI-OWLQOL relationship, so analyses were conducted for males and females separately. Adjusting for demographic confounders, baseline OWLQOL, and several worksite-level variables including intervention arm, a 1.9 unit decrease in BMI (the interquartile range) was associated with an OWLQOL increase of 1.7 (95 % CI: 1.2, 2.2) in males and 3.6 (95 % CI: 3.2, 4.0) in females. Similarly, a 23 unit increase in physical activity score was associated with an OWLQOL increase of 0.9 (95 % CI: 0.5, 1.4) in males and 1.6 (95 % CI: 1.0, 2.3) in females. Physical activity associations were attenuated when adjusting for change in BMI, but remained significant for women (mean BMI 27.8 kg/m(2)). CONCLUSIONS: This is the first study to demonstrate that increasing physical activity may improve obesity-specific QoL to a greater extent in women, particularly among overweight women, independent of BMI. Results may inform the design of interventions tailored to women targeting well-being through messages of increasing physical activity.

Dietary and physical activity behaviours related to obesity-specific quality of life and work productivity: baseline results from a worksite trial.

Obesity is associated with impaired health-related quality of life (QOL) and reduced productivity; less is known about the effect of dietary factors. The present study investigated how dietary behaviours, physical activity and BMI relate to weight-specific QOL and work productivity. The study was conducted in thirty-one small blue-collar and service industry worksites in Seattle. Participants were 747 employees (33·5 % non-White). Measures included self-reported servings of fruits and vegetables, dietary behaviours such as fast food consumption, Godin free-time physical activity scores, measured height and weight, Obesity and Weight-Loss QOL (OWLQOL) scores, and Work Limitations Questionnaire scores. Baseline data were analysed using linear mixed models separately for men (n 348) and women (n 399), since sex modified the effects. BMI was negatively associated with OWLQOL in both women (P < 0·001) and men (P < 0·001). The linear effect estimate for OWLQOL scores associated with a one-category increase in BMI was 30 (95 % CI 25, 44) % for women and 14 (95 % CI 10, 17) % for men. BMI was positively associated with productivity loss only in women (exp(slope) = 1·46, 95 % CI 1·02, 2·11, P = 0·04). Eating while doing another activity was negatively associated with OWLQOL scores in men (P = 0·0006, independent of BMI) and with productivity in women (P = 0·04, although the effect diminished when adjusting for BMI). Fast-food meals were associated with decreased productivity in men (P = 0·038, independent of BMI). The results suggest that obesogenic dietary behaviours and higher BMI are associated with decreased QOL and productivity to different degrees in women and men.

Recent physical activity in relation to DNA damage and repair using the comet assay.

BACKGROUND: Limited evidence suggests that very high-intensity exercise is positively associated with DNA damage but moderate exercise may be associated with DNA repair. METHODS: Participants were 220 healthy, Washington State 50- to 76-year-olds in the validity/biomarker substudy of the VITamins And Lifestyle (VITAL) cohort, who provided blood samples and completed questionnaires assessing recent physical activity and demographic and health factors. Measures included nested activity subsets: total activity, moderate- plus high-intensity activity, and high-intensity activity. DNA damage (n = 122) and repair (n = 99) were measured using the comet assay. Multivariate linear regression was used to estimate regression coefficients and associated 95% confidence intervals (CIs) for relationships between MET-hours per week of activity and each DNA outcome (damage, and 15- and 60-minute repair capacities). RESULTS: DNA damage was not associated with any measure of activity. However, 60-minute DNA repair was positively associated with both total activity (ß = 0.21, 95% CI: 0.0057-0.412; P = .044) and high-intensity activity (ß = 0.31, 95% CI: 0.20-0.60; P = .036), adjusting for age, sex, BMI, and current multivitamin use. CONCLUSIONS: This study is the first to assess broad ranges of activity intensity levels related to DNA damage and repair. Physical activity was unrelated to DNA damage but was associated with increased repair.

Recreational physical activity and risk of papillary thyroid cancer among women in the California Teachers Study.

PURPOSE: Little is known about the relationship between physical activity and thyroid cancer risk, and few cohort data on this association exist. Thus, the present study aimed to prospectively examine long-term activity and risk of papillary thyroid cancer among women. METHODS: 116,939 women in the California Teachers Study, aged 22-79 years with no history of thyroid cancer at cohort entry, were followed from 1995-1996 through 2009; 275 were diagnosed with invasive papillary thyroid cancer. Cox proportional-hazards regression provided relative risk (RR) estimates and 95% confidence intervals (CI) for associations between thyroid cancer and combined strenuous and moderate recreational physical activity both in the long-term (high school through age 54 years or current age if younger than 54 years) and recently (during the three years prior to joining the cohort). RESULTS: Overall, women whose long-term recreational physical activity averaged at least 5.5 MET-hours/week (i.e. were active) had a non-significant 23% lower risk of papillary thyroid cancer than inactive women (RR = 0.77, 95% CI: 0.57, 1.04). RR estimates were stronger among normal weight or underweight women (body mass index, BMI<25.0 kg/m(2), trend p = 0.03) than among overweight or obese women (trend p = 0.35; homogeneity-of-trends p = 0.03). A similar pattern of risk was observed for recent activity (BMI<25 kg/m(2), trend p = 0.11; BMI≥25 kg/m(2), trend p = 0.16; homogeneity-of-trends p = 0.04). Associations for long-term activity did not appear to be driven by activity in any particular life period (e.g. youth, adulthood). CONCLUSIONS: Long-term physical activity may reduce papillary thyroid cancer risk among normal weight and underweight women.