MECHANISM ENGINE
What Is Leptin?
Ghrelin gets all the attention because you feel it. Leptin’s the quieter one, and in some ways the more important one, because when it stops working properly, you can eat plenty and still feel like you’re running on empty.
The Broken Fuel Gauge
Leptin is released by fat cells and is meant to tell the brain, tank’s full, you’ve got reserves, you don’t need to eat right now. It’s a fuel gauge. In leptin resistance, the signal’s still being sent, the fuel’s still there, but the gauge in the brain stops reading it properly. The dashboard shows empty even when the tank is three quarters full. That’s why leptin resistance doesn’t feel like having plenty of energy stored. It feels like permanent, nagging hunger, regardless of how much fat is actually available to draw on.
Leptin is produced by fat cells in proportion to fat stores and signals satiety to the hypothalamus. In leptin resistance, often associated with excess visceral fat and chronic high insulin, the brain becomes less responsive to leptin’s signal despite leptin levels being adequate or high. The result is a mismatch between actual energy reserves and perceived hunger, which is one reason restrictive dieting alone often fails to hold long term.
Research on leptin resistance links it closely to insulin resistance and chronic inflammation, with improvements typically following changes that also improve insulin sensitivity, such as reduced UPF intake and regular movement, rather than leptin being targeted directly.
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Related mechanisms
Educational only, not medical advice. Speak to your GP before changing your fasting pattern, diet, or medication.
What this is based on
NHS and NICE guidance, cross-referenced against Neil’s own NHS blood test record going back to April 2012. See the full timeline and current numbers.