The purpose of this study was to assess how selected physiological and performance responses are affected when the normal increase in plasma free fatty acid concentration during exercise is blunted by ingesting nicotinic acid. On four occasions, 10 subjects cycled at 68 ± 1% VO2peak for 120 min followed by a timed 3.5-mile performance task. Every 15 min during exercise, subjects ingested 3.5 ml.kg LBM−1 of one of four beverages: 1) water placebo (WP), 2) WP + 280 mg nicotinic acid.l−1 (WP+NA), 3) 6% carbohydrate-electrolyte beverage (CE), and 4) CE+NA. Ingestion of nicotinic acid (WP+NA and CE+NA) blunted the rise in FFA associated with WP and CE; in fact, NA ingestion effectively prevented FFA from rising above rest values. The low FFA levels with NA feeding were associated with a 3− to 6-fold increase in concentrations of human growth hormone throughout exercise. The mean performance time for CE (10.7 min) was significantly less than for WP (12.2 min) and WP+NA (12.8 min), but did not differ from CE+NA (11.4 min). The results indicate that blunting the normal rise in FFA alters the hormonal response to exercise and reduces the capacity to perform high-intensity exercise.