Regulation of average 24 h human plasma leptin level; the influence of exercise and physiological changes in energy balance

Abstract

OBJECTIVE: The effects of short-term moderate physiological changes in energy flux and energy balance, by exercise and over- or underfeeding, on a 24 h plasma leptin profile, were investigated.

DESIGN: Subjects were studied over 24 h in four randomized conditions: no exercise\energy balance (energy intake (EI)=;energy expenditure (EE)=;11.8±0.8 MJ); exercise\energy balance (EI=;EE=;15.1±0.6 MJ); exercise\negative energy balance (EI=;11.8±0.8 MJ, EE=;15.1±0.8 MJ); exercise\positive energy balance (EI=;18.6±0.7 MJ, EE=;15.1±0.6 MJ).

SUBJECTS: Eight healthy, lean men (age: 23.5±7.0 y, body fat 14.1±5.4%, body mass index (BMI): 21.4±2.3 kg\m²).

MEASUREMENTS: Blood was sampled every hour during the daytime (09.00–23.00 h) and every two hours during the night (01.00–09.00 h) for analysis of plasma leptin, insulin, glucose, FFA and catecholamines.

RESULTS: Plasma leptin levels were highest around 01.00 h (mean±s.e.m. 4.9±2.0 ng\ml) and lowest around 11.00 h. (2.3±0.7 ng\ml). An increased 24 h EE, induced by exercise under conditions of energy balance, significantly decreased the peak and average 24 h plasma leptin concentration. A positive energy balance, by overfeeding, resulted in a significantly higher amplitude of the 24 h plasma leptin curve, compared to a condition of energy balance.

CONCLUSION: Exercise decreases peak and average 24 h plasma leptin concentration and a moderately positive energy balance increases the amplitude of the 24 h plasma leptin profile. These effects are not acute, but are manifest within 24 h. The variations of average 24 h FFA and average 24 h glucose concentrations almost fully explained the variation in average 24 h leptin concentration across trials.