Research paper
Friedman JM, Halaas JL. Leptin and the regulation of body weight in mammals. Nature. 1998 Oct 22;395(6704):763-70. doi:10.1038/27376. PMID: 9796811.
Why we cite it
The foundational review of the leptin system by its discoverer. Establishes leptin as the adipose-derived hormone that signals nutritional status to the brain and explains why most human obesity involves leptin resistance (high levels, impaired signaling) rather than leptin deficiency — making supplementation ineffective for typical obesity.