Decrease in serum leptin after prolonged physical activity in men.
OBJECTIVE
This study was designed to determine whether serum leptin levels were affected by a 5-d military course after 3 wk of combat training.


METHODS
26 male soldiers (mean age = 21 +/- 2 yr) were examined at the beginning of the training program and just at the end of the 5-d course. The combination of continuous heavy physical activity and sleep deprivation led to energy deficiency. Blood samples were analyzed for serum leptin, insulin, cortisol, adrenocorticotropin (ACTH), and testosterone; plasma was analyzed for free fatty acids (FFA), glycerol, glucose, and catecholamines.


RESULTS
At the end of the 5-d course, there was a significant reduction in serum leptin (0.40 +/- 0.04 ng x mL(-1) versus 1.47 +/- 0.14 ng x mL(-1), < 0.001), i.e., a mean decrease of 67.00 +/- 3.75%. Plasma norepinephrine and dopamine rose significantly from 296 +/- 17 ng x L(-1) to 672 +/- 48 ng x L(-1) and 23 +/- 3 ng x L(-1) to 40 +/- 5 ng x L(-1) ( < 0.001 and < 0.01, respectively), whereas epinephrine remained unchanged. Serum concentrations of the anabolic hormone, insulin, fell from 31.17 +/- 3.03 microU x mL(-1) to 17.79 +/- 1.58 microU x mL(-1) ( < 0.001), whereas plasma FFA and glycerol were increased ( < 0.001, < 0.05, respectively). A statistically significant correlation appeared between the changes in leptin and insulin (r = 0.5306, < 0.01). Serum testosterone decreased significantly ( < 0.001), whereas serum cortisol, ACTH, and plasma glucose were unchanged at the end of the course. The training program had no significant effect on mean body mass index.


CONCLUSIONS
A 4-wk strenuous military training program, which induced an energy deficiency, reduced serum leptin to a third of normal levels. The decrease in serum leptin was attributed to the exercise-induced elevation in catecholamines and hypoinsulinemia.
Gomez-Merino
Danielle
D
Department of Physiology, IMASSA-CERMA, Brétigny-sur-Orge, France. dgomez@imassa.fr
Chennaoui
Mounir
M
Drogou
Catherine
C
Bonneau
Dominique
D
Guezennec
Charles Yannick
CY
D000328:Adult; D002395:Catecholamines / Q000097:blood; D004734:Energy Metabolism / Q000502:physiology; D005227:Fatty Acids / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood*; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D013314:Stress, Mechanical; D016138:Walking / Q000502:physiology*
D002395:Catecholamines; D005227:Fatty Acids; D007328:Insulin; D020738:Leptin