Diets with low glycemic index minimized weight loss in rats reared in a simulation of microgravity by hindlimb suspension

One of the most important nutritional problems for humans during long-term space missions is loss of muscle mass. The most important of several causes of sarcopenia is the lack of stimulation of the muscles in the absence of gravity. The aim of this study was to evaluate the effect of diets with different glycemic indices (GI) on growth performance and body composition in rats reared in conditions of simulated microgravity. Forty male Sprague-Dawley rats were reared in 2 different conditions, one using traditional ground-based cages and the second using hindlimb suspension to simulate microgravity. The rats in each cage group were allocated to 1 of 2 different diets, matched for micro- and macronutrients, but with a different amylaceous fraction and, therefore, different GI in a 2 × 2 factorial design. Hindlimb suspension reduced food consumption, weight gain, and the weight of the soleus and gastrocnemic muscular masses. In rats fed with a low-GI diet, ghrelin concentration was significantly higher. In animals reared in conditions of microgravity with a low-GI diet reduced weight loss, and improved feed conversion ratio was observed. Results of this study show a potential benefit for a low-GI diet in conditions of simulated weightlessness.