High protein diet maintains glucose production during exercise-induced energy deficit: A controlled trial

Abstract

Background: Inadequate energy intake induces changes in endogenous glucose production (GP) to preserve muscle mass. Whether addition provision of dietary protein modulates GP response to energy deficit is unclear. The objective was to determine whether exercise-induced energy deficit effects on glucose metabolism are mitigated by increased dietary protein. Methods. Nineteen men ([mean SD] 23 2 y, VO2peak59 5 mlkg-1min-1) were divided into three groups, two consuming moderate (MP; 0.9 g protein kg-1 d-1), and one high (HP; 1.8 g protein kg-1 d-1) protein diets (55% energy from carbohydrate) for 11 days. Following 4 days of energy balance (D1-4), energy expenditure was increased for 7 days (D5-12) in all groups. Energy intake was unchanged in two, creating a 1000 kcal d -1 deficit (DEF-MP, DEF-HP; n = 6, both groups), whereas energy balance was maintained in the third (BAL-MP, n = 7). Biochemical markers of substrate metabolism were measured during fasting rest on D4 and D12, as were GP and contribution of gluconeogenesis to endogenous glucose production (f gng) using 4-h primed, continuous infusions of [6,6- 2H2]glucose (dilution-method) and [2-13C] glycerol (MIDA technique). Glycogen breakdown (GB) was derived from GP and fgng. Results: Plasma -hydroxybutyrate levels increased, and plasma glucose and insulin declined from D4 to D12, regardless of group. DEF-MP experienced decreased plasma GP from D4 to D12 ([mean change SD] 0.24 0.24 mgkg-1min-1), due to reduced GB from D4 (1.40 0.28 mgkg-1min-1) to D12 (1.16 0.17 mgkg-1min -1), P < 0.05. Conversely, BAL-MP and DEF-HP sustained GP from D4 to D12 ([mean change SD] 0.1 0.5 and 0.0 0.2 mgkg-1min-1, respectively) by maintaining GB. Conclusion: Exercise-induced energy deficit decreased GP and additional dietary protein mitigated that effect. © 2011 Smith et al; licensee BioMed Central Ltd.