Effects of high- and low-carbohydrate meals on maximum exercise performance in chronic airflow obstruction

The purpose of this study was to compare the effects of isocaloric liquid meals with high fat (55 percent) and low carbohydrate (28 percent) content (Pulmocare) to meals with low fat (30 percent) and high carbohydrate (53 percent) content (Ensureplus) on exercise performance in subjects with chronic airflow obstruction (CAO). Twelve stable subjects with CAO (FEV1 = 1.30 +/- 0.47 L) underwent incremental symptom-limited exercise tests 90 minutes following the ingestion of 920 calories of EnsurePlus HN (E), 920 calories of Pulmocare (P), or a noncaloric placebo (C). Tests were performed on three days, in a double-blind randomized fashion. Expired gases were collected continuously and analyzed every 30 seconds. The mean maximal work load after E (81 +/- 24 W) was significantly less than that after P (88 +/- 21 W) or C (88 +/- 24 W). The mean ventilation at exhaustion was similar after E (48 +/- 13 L/min), P (51 +/- 11 L/min), and C (49 +/- 10 L/min). In comparison to C, six of the 12 individuals had a decreased work load following E, while only one had a decreased maximal tolerated work load following P. The results of this study suggest that meals with a higher fat and lower carbohydrate content may be less likely to impair work performance of patients with CAO in the absorptive phase than meals with a lower fat and higher carbohydrate content. These findings may have clinical significance to patients with CAO who complain of postprandial exertional dyspnea.