Restores fullness signal
Leptin
Also searched as Leptin.
More is not better. In the rare people who make none, replacing it is transformative; in common obesity leptin is already high and the brain has stopped listening.
In depth
The satiety hormone from fat tissue. The decisive fact: in common obesity leptin is high, not low — the problem is resistance to the signal, so replacement logic fails. The evidence shows the case where it worked and the disqualifier beside it.
What drives it
Supports weight management increases it.
10.3389/fendo.2023.1172060 — The loop that makes the resistance story coherent. Leptin is synthesized and secreted by adipocytes in proportion to fat mass — so adiposity raises leptin, and in common obesity leptin is high precisely because there is more fat reporting. This link explains why people with obesity have plenty of a hormone that lowers weight. doi 10.3389/fendo.2023.1172060
Sleep increases it.
Sleep deprivation has been associated with multiple physiological changes, including increased cortisol and ghrelin levels, decreased leptin levels and impaired glucose metabolism. The pairing is the point: leptin down and ghrelin up simultaneously - satiety signal falls while hunger signal rises. Not one lever, two moving in opposite directions. doi 10.1016/j.smrv.2011.05.001 · PMC3132857
Obesogen exposure reduces it.
body fat, plasma hormones and visceral white adipose tissue methylome and transcriptome collectively indicate that the F4 obesity is consistent with a leptin resistant, thrifty phenotype. PMID 29222412
What it drives
It reduces Supports weight management.
The human proof is monogenic and about as clean as biology gets: two consanguineous sisters with a homozygous LEP missense mutation and undetectable serum leptin despite markedly elevated body fat. Twelve months of recombinant leptin took BMI from 59 to 38 and from 60 to 48 kg/m2, normalized serum lipids, improved insulin sensitivity, and reversed hypogonadotropic hypogonadism with menstruation resuming. One missing protein, one replacement, and the entire phenotype unwinds. And the conditional is the whole commercial story: this does not transfer to common obesity. In common obesity leptin is already high and the brain has stopped reading it. The trial record is a list of attempts — pegylated leptin in obese men, three dosing schedules of methionyl leptin, leptin after gastric bypass, metreleptin in the low-leptin subgroup — and recombinant leptin did not improve insulin action in obese people with type 2 diabetes. Anything marketed on the ob/ob mouse photograph is selling a rare-disease result to a common-disease audience. And a dissection most accounts miss: in leptin-deficient mice, calorie restriction still produced the full compensatory fall in energy expenditure — 17 percent below predicted by day, 52 percent at night — with NO leptin present at all. Leptin is not required for compensatory reduction in energy expenditure, but the hyperphagia of the weight-reduced state is leptin-dependent. The regain response has two halves and leptin owns the hunger half only — which is why the leptin → appetite link is drawn separately here. doi 10.1530/EC-25-0521 · PMC12118419
It increases Curbs appetite.
10.1530/JOE-14-0480 — drawn separately from the Leptin Signaling → Weight & Body Fat link on purpose, because the leptin-deficient mouse experiment separates them: the hyperphagia of the weight-reduced state is leptin-dependent while the compensatory drop in energy expenditure is not. In the human monogenic cases the presenting complaint is intense hunger and hyperphagia from childhood, and that is what replacement resolves first. doi 10.1530/JOE-14-0480
It increases Appetite receptor signaling.
Nothing in this project has been named that often. This edge is the mechanism of the whole leptin story: leptin, which is produced in adipose tissue, binds to the leptin receptor on pro-opiomelanocortin-expressing neurons in the hypothalamus, and POMC-derived melanocortin peptides reduce food intake and body weight by acting as endogenous ligands for the brain-expressed MC4R. Leptin does not act on fat — it acts on this switch. If the downstream switch is intact, more leptin does nothing. PMID 33137293 · PMC5641599
It increases Fasting insulin.
insulin, fasting insulin, type 2 diabetes and blood lipids share one literature: heart, kidney, liver, and metabolic diseases share interlinked pathological mechanisms, including inflammation, oxidative stress, insulin resistance, and endothelial health issues. These four overlap by nature: fasting insulin is the level, insulin is the signaling, type 2 diabetes is the diagnosis and blood lipids are the substrate. The same driver legitimately reaches all four, and a reader should not mistake four arrows for four independent findings. doi 10.1038/s41581-026-01066-0 · PMC11725408
It increases Type 2 diabetes.
insulin, fasting insulin, type 2 diabetes and blood lipids share one literature: heart, kidney, liver, and metabolic diseases share interlinked pathological mechanisms, including inflammation, oxidative stress, insulin resistance, and endothelial health issues. These four overlap by nature: fasting insulin is the level, insulin is the signaling, type 2 diabetes is the diagnosis and blood lipids are the substrate. The same driver legitimately reaches all four, and a reader should not mistake four arrows for four independent findings. doi 10.1038/s41581-026-01066-0 · PMC11725408
It increases Lowers cholesterol.
insulin, fasting insulin, type 2 diabetes and blood lipids share one literature: heart, kidney, liver, and metabolic diseases share interlinked pathological mechanisms, including inflammation, oxidative stress, insulin resistance, and endothelial health issues. These four overlap by nature: fasting insulin is the level, insulin is the signaling, type 2 diabetes is the diagnosis and blood lipids are the substrate. The same driver legitimately reaches all four, and a reader should not mistake four arrows for four independent findings. doi 10.1038/s41581-026-01066-0 · PMC11725408
It reduces Hunger hormone.
Leptin and ghrelin are opposing arms of appetite regulation.
It increases Reproductive trigger hormone.
Leptin, an anorexigenic adipokine secreted by white adipose tissue reflective of total body energy stores, is a permissive signal requisite for healthy GnRH neuronal function. doi 10.1152/physrev.00015.2024 · PMID 23550015 · PMC3786537
Blends that modulate it
Each blend page names this pathway and carries the study behind its claim.
See it on the map
Open the causal map to follow this pathway upstream and downstream, arrow by arrow, each with its study.