From storage depot to broadcasting station
For most of medical history fat was viewed as passive padding — a place to stash extra calories. That picture broke when researchers discovered that adipose tissue secretes hormones of its own, collectively called adipokines. Fat, it turns out, is a true endocrine organ that constantly broadcasts a status report on the body's fuel reserves to the brain, liver, muscle and immune system.
The headline adipokine is leptin. Roughly speaking, the more fat a person carries, the more leptin they release, so circulating leptin is a long-term signal of how full the energy stores are. When it reaches the brain, leptin reduces appetite and permits energy expenditure — the body's way of saying, “reserves are healthy, you can ease off eating.” When fat stores fall during prolonged fasting, leptin drops sharply, and the resulting hunger and metabolic slowdown defend the body against starvation. Leptin therefore sits at the center of energy homeostasis.
The other voices: adiponectin and the inflammatory tilt
If leptin reports *quantity*, adiponectin reports something closer to *quality*. It improves the body's sensitivity to insulin and has anti-inflammatory effects, and — counterintuitively — its levels fall as fat mass rises. So lean, metabolically healthy people tend to have high adiponectin, while excess fat is marked by low adiponectin and growing insulin resistance. Other adipokines such as resistin and various inflammatory signals tend to rise with fat mass, tilting the whole environment toward inflammation.
Putting these together explains a clinical pattern. As fat accumulates, the adipokine mix shifts: leptin climbs but is heard poorly, adiponectin falls, and inflammatory signals rise. The net result drags tissues toward insulin resistance — a chain that links excess fat, type 2 diabetes and cardiovascular risk. Fat is not merely *where* the calories sit; through its hormones it actively shapes how the rest of the body handles fuel.