Leptin is a satiety factor in rodents. Mice unable to produce
leptin or with abnormal receptors are obese. The administration
of leptin results in weight loss with defective production.
In obese humans, however, leptin levels are elevated, consistent
with greater fat tissue. In general, the elevated leptin levels
decrease with weight loss. It is possible that this decrease
in leptin increases appetite and consequent weight regain. Leptin
is limited in its therapeutic effectiveness because obese individuals
exibit marked resistance to the appetite-reducing effects of
Considine RV, Sinha MK, Heiman ML, Kriauciunas A, Stephens
TW, Nyce MR, et al. Serum immunoreactive-leptin concentrations
in normal-weight and obese humans. N Engl J Med 1996;334:292-5.