OBJECTIVE: To investigate possible relationships between leptin and energy
expenditure (EE), both in the condition of stable body weight and during we
ight loss.
SUBJECTS: Seventy four Caucasian, adult obese women with stable body weight
(including 10 obese women studied before and during a body weight-reducing
program).
MEASUREMENTS: Resting EE (REE) and substrate oxidation rates by indirect ca
lorimetry; plasma leptin concentrations by radioimmunoassay (RIA).
RESULTS: In conditions of stable body weight, leptin values showed a signif
icant, negative relationship with REE, as expressed in absolute values (P =
0.030) and as adjusted for the variation in lean body mass (LBM) (P = 0.01
7). This negative relationship was independent of both LBM and fat mass (FM
). Linear regression analysis was used to obtain the equation linking REE a
nd LBM; then both predicted REE and the percent deviation from predicted RE
E were calculated for each subject. Leptin values were negatively related (
P < 0.0001) to the deviation from predicted REE. During active body weight
loss, the modifications of both REE (Delta REE) and lipid oxidation (Delta
lipid oxidation) were significantly negatively related to leptin concentrat
ions, which were measured before the dieting period (P < 0.03 for both).
CONCLUSION: In obese women, high plasma leptin concentrations are associate
d with a low rate of REE, when body weight is stable, and with a reduction
of REE and lipid oxidation, in response to a hypocaloric diet. This suggest
s that, in severely obese women, leptin is a marker of sparing energy mecha
nisms operating in both basal and reducing weight conditions.