The role of phosphorus in diet-induced thermogenesis of lean male subjects -

Abstract

Energy Expenditure (EE) is the sum of resting metabolic rate (RMR), diet-induced thermogenesis (DIT) and energy expended on physical activity. Diet-induced thermogenesis is the increase that takes place in EE after ingestion of food, noting that this increase is above the RMR and accounts for 5percent to 15percent of total EE. This increase can be largely related to the increased production of ATP which is used to cover the cost of digestion, absorption, transport and storage of the ingested food. Proteins have the highest thermic effect (20percent-30percent) compared with carbohydrates (5percent-10percent) and fats (0percent-3percent). Moreover, proteins contain high quantity of phosphorus that is required for energy production through the synthesis of ATP. However, it is not clear whether the high thermogenesis of proteins is affected by their content of phosphorus. Thus, the aim of the present study was to explore the impact of phosphorus ingestion on DIT and substrate oxidation of healthy lean male subjects consuming two isocaloric meals, a normal protein-low phosphorus meal and a high protein-low phosphorus meal using a low phosphorus containing protein, egg white. This is a single-blind, randomized, and placebo-controlled crossover study that was conducted on healthy lean male subjects who were randomly allocated into two experiments, 12 subjects each, a normal-protein meal experiment (15percent of total E from protein) and a high-protein meal experiment (50percent of total E from protein). Overnight fasted subjects undertook 2 sessions separated by a minimum of one week and were asked to consume the appropriate meal with phosphorus (500 mg) or placebo tablets in a random order. Energy expenditure, percent fat oxidation, percent carbohydrate oxidation and respiratory quotient (RQ) were measured at baseline and for the next four hours following meal consumption in a period of 15 minutes interval with 15 minutes break, using a ventilated hood and canopy system (COSMED QUARK CPET UNIT) for indirect calorimetry measurement. Urine was collected at the end of the experimental per