LEPTIN CONCENTRATIONS EXPERIENCE A DELAYED REDUCTION AFTER ACUTE HEAVY RESISTANCE EXERCISE

Abstract

Leptin is an important metabolic hormone providing the brain with information concerning energy balance. Most studies have reported that circulating leptin concentrations are unaltered by acute, moderate exercise. We hypothesized that these studies have been limited by short sampling schemes (< 4 hrs) post-exercise and may have missed a time-delayed reduction in circulating leptin concentrations. This hypothesis was tested by sampling venous blood for 13 hrs during two conditions: control and post-exercise. Ten men (21 ± 1 yrs, 177 ± 2 cm, 79 ± 3 kg, 11 ± 1%BF, 51 ± 1 mlòkgòmin-1) completed an acute heavy resistance exercise bout (50 total sets comprised of the squat, bench press, leg press, and lat pulldown) from1500 to 1700 hr. Blood was sampled post-exercise hourly until 0600 hr the next morning and also during a time-matched control period. Leptin concentrations were measured by an immunoradiometric assay. Resting metabolic rate (RMR) was measured upon awakening for each condition. Overall, there were no significant differences between the control and exercise conditions. However, interaction effects indicated that serum leptin concentrations were lower post-exercise at hrs 9 (2.9 vs. 2.2 ng/ml), 10 (2.7 vs. 2.0 ng/ml), 12 (2.5 vs. 1.8 ng/ml), and 13 (2.6 vs. 1.8 ng/ml). This delayed reduction was accompanied by a 12% elevation in morning-after RMR (0.25 ± .02 vs. 0.28 ± .02 Lòmin-1). We conclude that leptin concentrations experience a delayed (9 hrs) reduction in the systemic circulation following acute resistance exercise. This decline is likely associated with the energy cost of the exercise bout and is not due to losses in fat mass. Supported in part by an ACSM Foundation Research Grant to BCN