Resumen de A 28-Day Carbohydrate-Restricted Diet Improves Markers of Cardiometabolic Health and Performance in Professional Firefighters

Hunter S. Waldman, JohnEric W. Smith, John G. Lamberth, Brent J. Fountain, Matthew J. McAllister

• We investigated the effects of a 4-week ad-libitum, nonketogenic, carbohydrate-restricted (<25% of calories) diet (CRD) on cardiometabolic and performance markers in firefighters (FF). Subjects (n = 15) completed 9 sessions (trials 1-3 [familiarization], trials 4-6 [baseline], and trials 7-9 [post-CRD]). Following habitual western diet, anthropometric measures were assessed, glucose tolerance measured, and then completed a graded cycling test, maximal Wingate test, and conducted their FF physical performance assessment (FPPA) to measure performance while metabolic variables and perceptual responses were recorded. Subjects then adhered to a CRD for a 4-week duration and returned for repeat testing. Body fat as measured by BodPod, and 7-site skinfold thickness decreased (p < 0.01), and a decrease was observed in blood pressure (BP) (p < 0.01; ~5 mm Hg) after CRD. There were no differences found for glucose tolerance, but an increase was found for fat oxidation rates (p < 0.01; ~0.07 g[middle dot]min-1) and a decrease in carbohydrate oxidation rates across a range of intensities (p < 0.01; ~0.24 g[middle dot]min-1). Finally, the 2.41-km run and pull-up performance during the FPPA improved (p < 0.01; ~41 second and 3 repetitions, respectively) and with no differences observed between treatments regarding the Wingate test. To date, this is the first CRD implemented with FF and resulted in decreased fat mass (~2.4 kg), BP, and improvements to performance on the FPPA while preserving high-intensity exercise. These data suggest that a 28-day CRD can benefit markers of health in professional FF without detriments to occupational performance.