Acute Effects of Daily Step-Count on Postprandial Metabolism and Resting Fat Oxidation: A Randomized Controlled Trial

To examine the effects of daily step-count on same-day fat oxidation and postprandial metabolic responses to an evening high-fat mixed meal (HFMM). Ten healthy participants (5 females, 30±7 y) completed four different daily step-counts - 2,000 (2K), 5,000 (5K), 10,000 (10K), and 15,000 (15K) steps - on separate days in randomized order. On experimental days, participants ate the same meals and walked all steps on an indoor track at a pace of 100 steps/min in three roughly equal bouts throughout the day. After the final walking-bout, participants' resting energy expenditure (REE), respiratory exchange ratio (RER), and fat oxidation rate (FAT ) were measured. Blood samples were obtained before (BL) and 30-, 60-, 90-, 120-, and 240-minutes following consumption of a HFMM (960 kcal; 48% fat) to measure triglycerides (i.e., postprandial lipemia; PPL), non-esterified fatty acids (NEFAs), insulin, and glucose. Two-way ANOVAs indicated condition effects where PPL was significantly higher after 2K versus 10K (+23±8 mg/dL, =0.027), and NEFAs were significantly higher after 15K versus 2K (+86±23 µmol/L; =0.006). No differences were found for insulin, glucose, or REE among conditions (all >0.124). Similarly, RER ( =0.055; η =0.24) and FAT ( =0.070; η =0.23) were not significantly different among conditions. In young adults, 10K steps elicited the greatest decrease in PPL, an established cardiovascular disease risk factor. NEFA levels were highest after the 15K condition, likely due to alterations in adipose tissue lipolysis or lipoprotein lipase activity with increased activity.