Exercise Effects on Fecal pH During A Period of Excess Dietary Fat and Sugar Consumption

Abstract

BackgroundShort chain fatty acids (SCFA), a product of microbial fermentation, have been observed in higher quantities in obese individuals compared to lean counterparts. Despite links between excess caloric consumption and adiposity, data are limited on whether fecal pH correlates with changes in body fat during periods of excess fat and sugar consumption and how exercise influences these relationships.PurposeThe goal of this study was to assess whether changes in fecal pH (a proxy for SCFA production) correlated with changes in measures of adiposity during a fat‐sugar supplemented diet and exercise intervention.MethodsTwelve otherwise healthy overweight/obese males (aged 18–50 years; BMI = 29.6±3.6 kg/m2; percent body fat = 31.9±5.1%) consumed 12 donuts/wk for 4 weeks which contributed an excess energy intake of 14,554 kcal. Participants were randomized to 3 groups: moderate‐intensity continuous training (MICT), high‐intensity interval training (HIIT), and no exercise (Control). Body mass index (BMI) and percent body fat (% fat) were assessed pre‐ and post‐intervention by Seca stadiometer‐scale and DEXA respectively. Baseline and 4‐week fecal samples were obtained from participants and fecal pH measured using a digital pH meter. Spearman correlations were used to assess correlations between changes in fecal pH, BMI and % fat. The Wilcoxon rank sum test was used to evaluate differences in fecal pH between groups.ResultsMean fecal pH at baseline was 6.52±0.33. Median (IQR) changes in pH for control, HIIT and MICT groups (0.22 (−0.33, 0.39), 0.22 (−0.80, 0.55), −0.33 (−0.70, −0.08), respectively) did not differ significantly (p=0.375). Although mean % fat did not change significantly in any group, the change in fecal pH across all groups during the intervention was positively correlated with the change in % fat (r=0.69, p=0.013). No correlation was observed between changes in fecal pH and BMI (r=−0.44, p=0.155).ConclusionsFindings from this study suggest that an increase in fecal pH was associated with an increase in percent body fat. These positive changes in adiposity during a period of increased fat and sugar intake suggest that further work is needed to understand the role of gut microbes and SCFA concentrations on body composition over time. Further, these findings suggest a need to understand how different exercise modalities mediate associations between gut SCFA production and changes in body fat. Finally, fecal pH as a proxy for SCFA production in the colon may be a risk marker for weight change during periods of fat‐sugar overfeeding.