The paradox of leptin resistance
Here is the puzzle that ties the whole track together. Leptin should suppress appetite, and people with obesity have plenty of fat and therefore very high leptin. So why are they still hungry? The answer is leptin resistance: the brain stops responding properly to leptin, much as tissues can stop responding to insulin. High leptin no longer reads as “stores are full.”
This is why injecting leptin does not cure common obesity — the system is already shouting and not being heard. It also explains the cruelty of weight loss: as fat drops, leptin falls, and the still-listening famine alarm fires hard, defending the higher weight. The body's set point has drifted up and now resists coming back down.
From fat to the whole body: the metabolic syndrome
Excess fat, especially around the abdomen, does not stay quiet. As we saw, it shifts its adipokine output — protective adiponectin falls, inflammatory signals rise — and dumps fatty acids into the blood. Together these drive insulin resistance, the soil from which type 2 diabetes grows. The same process raises blood pressure and disturbs blood lipids.
When several of these travel together, clinicians call it the metabolic syndrome — a cluster, not a single disease, that sharply raises the risk of diabetes and heart disease.
Metabolic syndrome — a cluster (≈3 of 5):
[ ] Large waist circumference (central fat)
[ ] High triglycerides
[ ] Low HDL ("good") cholesterol
[ ] High blood pressure
[ ] High fasting blood glucose
Common root: excess central fat → insulin resistance
Endpoint risk: type 2 diabetes + cardiovascular diseaseWorking with the system, not against it
If weight is defended by a control loop, durable change means shifting the loop, not out-muscling it. This is the logic behind modern obesity medicine. Drugs based on GLP-1 — a gut hormone you will meet in the appetite-and-gut track — act on the very brain circuits we mapped, lowering the defended set point so that eating less feels natural rather than like constant deprivation.