McDonough, Daniel J.

OBJECTIVE To test the effect of physical activity on the gut microbiome and circulating short-chain fatty acids (SCFAs) among sedentary adults with prediabetes and overweight or obesity. RESEARCH DESIGN AND METHODS In a pilot and feasibility trial, we randomized 77 adults with prediabetes and a sedentary lifestyle into one of two groups: 1) intervention: invited to engage in home-based moderate-intensity walking 3×/week for 30 min/session in weeks 1–4 and for 45 min/session during weeks 5–8 of the 8-week intervention; or 2) control: maintained habitual physical activity levels. We performed metagenomic sequencing from stool collected at baseline, week 4, and week 8, with SCFAs measured from serum collected at baseline and week 8. Taxonomic and functional profiling was performed on the metagenomic reads; α-diversity metrics were subsequently derived. Linear regression assessed the difference in change between the intervention and control groups for α-diversity and SCFA levels. RESULTS We screened 1,533 participants for eligibility and consented 132. Of these, 87 entered the run-in phase, and 77 were randomized. Participants were mean (SD) 51.4 (8.9) years old, 87.7% female, and 74% non-Hispanic White. Mean fasting glucose was 103.3 (13.2) mg/dL, while mean BMI was 34.4 (5.7) kg/m2. Compared with the control group, the intervention group experienced decreased α-diversity as characterized by Shannon, Richness, and Faith diversity indices by intervention week 8 (P < 0.05). Changes in SCFA levels were not statistically significant different in intervention versus control. CONCLUSIONS Randomization to a walking intervention resulted in modest gut microbiome changes among adults with overweight or obesity and prediabetes.

Background: The prevalence of non-alcoholic fatty liver disease (NAFLD) in U.S. adults is over 30%, yet the role of lifestyle factors in the etiology of NAFLD remains understudied. We examined the associations of physical activity, by intensity and type, and television viewing with prevalent NAFLD. Methods: Cross-sectional analysis of a population-based sample of 2726 Black (49%) and White (51%) adults (Mean (SD) age, 50 (3.6) years; 57.3% female) from the CARDIA study. Exposures were aerobic activity by intensity (moderate, vigorous; hours/week); activity type (aerobic, muscle-strengthening; hours/week); and television viewing (hours/week), examined concurrently in all models and assessed by validated questionnaires. Our outcome was NAFLD (liver attenuation < 51 Hounsfield Units), measured by non-contrast computed tomography, after exclusions for other causes of liver fat. Covariates were sex, age, race, study center, education, diet quality, smoking status, alcohol consumption, and body mass index or waist circumference. Results: 648 participants had NAFLD. In the fully adjusted modified Poisson regression model, the risk ratios per interquartile range of each exposure were moderate-intensity aerobic activity, 1.10 (95% CI, 0.97–1.26); vigorous-intensity aerobic activity, 0.72 (0.63–0.82); muscle-strengthening activity, 0.89 (0.80–1.01); and television viewing, 1.20 (1.10–1.32). Relative to less active participants with higher levels of television viewing, those who participated in ≥2 h/week of both vigorous-intensity aerobic and muscle-strengthening activity and <7 h/week of television viewing had 65% lower risk of NAFLD (risk ratio = 0.35, 95% CI = 0.23–0.51). Conclusion: Adults who follow public health recommendations for vigorous-aerobic and muscle-strengthening activity, as well as minimize television viewing, are considerably less likely to have NAFLD than those who do not follow the recommendations and who have relatively high levels of television viewing.

Introduction: The prevalence of nonalcoholic fatty liver disease (NAFLD) in US adults is over 25%, yet the etiology of lifestyle factors in the development of NAFLD remains understudied. We examined the independent and joint associations among aerobic physical activity (PA) intensity (moderate, vigorous) and PA type (aerobic, muscle strengthening), television viewing (TV), and odds of NAFLD. Hypothesis: Higher levels of aerobic and muscle strengthening PA are associated with lower odds of NAFLD, and higher levels of TV are associated with higher odds of NAFLD. Methods: We analyzed data from Year 25 of the CARDIA cohort study. Our exposures (moderate and vigorous aerobic and muscle strengthening PA, TV; hr/wk) were assessed using validated questionnaires. Our outcome (NAFLD) was measured using non-contrast computed tomography. We constructed multivariable logistic regression models to examine the independent and joint associations between PA (moderate or vigorous aerobic and strength), TV, and odds of NAFLD. Covariates were sex, age, race, study center, education, diet, smoking status, alcohol consumption, and waist circumference. Results: 2726 participants (648 with NAFLD) were analyzed (mean (SD) age, 50.1 (3.6) years; 49% Black; 43% male). Fully adjusted odds ratios per IQR-standardized continuous PA and TV were: moderate aerobic PA (IQR = 4.3), 0.93 (95% CI, 0.81-1.07); vigorous aerobic PA (IQR = 1.9), 0.63 (95% CI, 0.55-0.73); muscle strengthening PA (IQR = 3.3), 0.80 (95% CI, 0.07-0.92); and TV (IQR = 14.0), 1.20 (95% CI, 1.10-1.32). Only vigorous aerobic PA remained statistically significant after waist circumference adjustment, 0.83 (95% CI, 0.70-0.98). A PA-TV index model (Figure) indicated the combination of higher vigorous aerobic and muscle strengthening PA and lower TV resulted in an odds ratio of 0.23 (95% CI, 0.15-0.37). Conclusion: Concurrent higher levels of vigorous aerobic PA (≥2 hr/wk), muscle strengthening PA (≥2 hr/wk), and lower levels of TV (<7 hr/wk) were associated with 77% lower odds of NAFLD.