Higher Protein Diet Suppresses Appetite at High Altitude

Abstract

Higher‐protein (>0.8 g protein/ kg body weight/d, <35% total energy intake) diets facilitate weight loss at sea level (SL) in part by suppressing appetite and preserving lean body mass. Though these effects are beneficial during intentional weight loss, protein‐mediated appetite suppression may be detrimental if extant during periods of unintentional weight loss such as those common during sojourns at high altitude (HA). This study aimed to determine the effect of higher protein diets on appetite during HA sojourn. Following a 22d free‐living SL period during which body weight was maintained and volunteers were instructed to consume 1.0 g protein/kg/d, 17 healthy, unacclimated males ([mean ± SD] 23.4 ± 5.6 yr, BMI 26.2 ± 3.6 kg/m2) were randomly assigned to consume diets moderate (1.0 g protein/kg/d, 45% carbohydrate) or higher (2.0 g/kg/d, 45% carbohydrate) in protein, and then ascended to and resided at HA (4300m, Pikes Peak, CO) for 22d. At HA, volunteers subsisted on controlled energy restricted diets providing 70% of SL weight maintenance energy needs, and engaged in prescribed physical activity to induce a 40% total daily energy deficit. Subjective ratings of hunger (H), fullness (F), prospective consumption (PC) and desire to eat (DE) were measured on SL day 13, and HA days 2 and 19 by visual analog scales administered hourly after waking and every 2 min during three meals consumed at a self‐selected pace. Each volunteer consumed the same customized meals and snacks at prescribed times on each of the three days. Total weight loss during HA was −7.9 ± 1.9 kg and did not differ by diet (P‐interaction = 0.64). H, PC, and DE measured both during meals and hourly were lower on HA‐d2 relative to SL (P < 0.05) but did not differ by diet, whereas hourly F was higher (P < 0.05) and did not differ by diet, indicating that appetite was suppressed on HA‐d2 independent of protein intake. On HA‐d19, H, F, PC and DE measured during meals did not differ from SL or from HA‐d2, and did not differ by diet. In contrast, differences between hourly appetite ratings measured on HA‐d19 and those measured at SL and on HA‐d2 were diet‐dependent (diet‐by‐day interaction, P < 0.05). With moderate protein, hourly H, PC, and DE were higher and hourly F was lower on HA‐d19 relative to HA‐d2 (P < 0.05), but did not differ from SL despite prolonged energy deficit. Conversely with higher protein, hourly H, PC, and DE remained lower, and hourly F remained higher than SL on HA‐d19 (P < 0.05). These findings are consistent with rapid appetite suppression upon ascent to HA that appears to diminish, but not fully recover after 17 days of acclimation. That appetite remained suppressed to a greater extent in those consuming higher‐protein diets suggests that such diets could be counterproductive during HA sojourns by contributing to unintentional weight loss. Nutritional regimens for HA sojourns should consider that appetite‐suppressing effects of higher‐protein diets may offset potential favorable effects of such diets for preserving lean body mass during HA‐induced energy deficit. The views expressed in this abstract are those of the authors and do not reflect Dept of Army, Dept of Defense, or U.S. Government official policy.Support or Funding InformationU.S. Army Medical Research and Materiel Command