Effect of Carbohydrate-rich and Fat-rich Diet on Exercise Tolerance and Gas Exchange in Stable COPD Patients: A Randomized Controlled Trial

Background and objectives: Malnutrition in chronic obstructive pulmonary disease (COPD) is linked to poor exercise tolerance.As there is limited data on the effect of dietary changes in COPD, this study aimed to evaluate the effect of 2-week dietary intervention on exercise tolerance measured by distance covered in 6-minute walk test (6MWT), Borg dyspnea scale, and gas exchange parameters like minute ventilation (MV), volume of maximal exhaled carbon dioxide (VCO 2 max), volume of maximal oxygen consumption (VO 2 max,) VO 2 /kg, and respiratory quotient (RQ) in stable COPD patients.Methods: This randomized controlled trial was conducted on 90 stable COPD patients randomized into three groups (control group, fat-rich diet group, and carbohydrate-rich diet group) as 1:1:1 ratio, and individualized diet plan for 2 weeks was tailored and issued by the dietitian based on the data obtained from the diet history.Six-minute walk test and cardiopulmonary exercise testing were repeated after 2 weeks of dietary intervention and compared with baseline.All the statistical analyses were carried out at 5% level of significance, and p-value less than 0.05 was considered to be significant.Results: The baseline mean 6MWT had no significant difference between the groups.The overall mean increase in the 6MWT distance after the dietary intervention was 6.9 meters, with no statistically significant difference between groups in both the 6MWT (p = 0.23) and Borg dyspnea scale (p = 0.56).The RQ analysis revealed a significant difference in postintervention RQ between control and carbohydrate-rich diet groups (p = 0.02).But other gas exchange parameters had no significant difference between the groups. Conclusion:In this study we concluded that the exercise performance, indicated by 6-minute walk distance (6MWD), did not improve across the groups regardless of the dietary composition with no significant differences between the groups.However, the high-carbohydrate and low-fat diet significantly increased the RQ but had no significant effect on other gas exchange parameters and exercise performance.