Responses to exercise, fluid, and energy balances during Ramadan in sedentary and active males

This study compares the effects of the Ramadan fast (RF) on body and plasma compositions, hematology, and responses to steady state submaximal exercis e in six physically active (A, 35.5 +/- 1.6 y) and seven sedentary (S, 37.6 +/- 2.3 y) Kuwaiti men. Subjects were evaluated: 1) 1 wk before RF (pre-RF ); 2) 2 wk after the start of RF (mid-RF); 3) at the 4th wk of RF (end-RF). Total body weight and body fat decreased insignificantly (<1.5%, P > 0.3) in both groups. At the end of Ramadan, significant increases in osmolarity (P < 0.05), Na (P < 0.05) and bicarbonate (P < 0.05), and a decrease in ser um iron were noted in sedentary but not in active subjects. Platelet count was lower in both groups by the end of RF (P < 0.05). Body weight and perce nt fat changed little (<1.5%) in either group. During RF, submaximal exerci se heart rate declined insignificantly in group S but significantly (P < 0. 05) in group A. The respiratory exchange ratio R during steady state submax imal exercise decreased markedly (P < 0.001) by the end of RF in both group s. It is concluded that energy balance is well maintained during RF both in S and in A subjects. Metabolic adaptations during RF result in lower exerc ise R due to increased Lipid usage. Deficits or redistribution of specific micronutrients (iron, vitamins) may account for reductions in serum iron an d platelet counts, particularly in sedentary subjects that need to limit in take to maintain body weight. The decrease in submaximal exercise heart rat e indicates that during RF, cardiovascular adaptation to conditioning is ad equate in the more physically active group. Body fluid balance was better m aintained in active than in sedentary subjects. Nutrition 1999;15:735-739. (C) Elsevier Science Inc. 1999.