Fat storage & fat burning (how fat is managed)
Body fat is a fuel tank. Whether you deposit into it or draw from it is governed almost entirely by hormones and energy balance — not by the fat you eat in isolation. This is the physiology every fat-loss protocol is really acting on.
How it works
- Storage (lipogenesis) — in the fed, high-insulin state, glucose and dietary fat are packaged into triglycerides and stored in fat cells (adipocytes).
- Mobilisation (lipolysis) — when insulin falls and adrenaline rises (fasting, exercise), stored triglycerides are split into free fatty acids + glycerol and released into the blood.
- Transport & burning (beta-oxidation) — free fatty acids travel to muscle, enter the mitochondria (helped by carnitine) and are oxidised for ATP via the aerobic system.
- The gatekeeper is insulin: high insulin blocks lipolysis, so fat is burned mainly when insulin is low and demand is high.
Why it matters
Fat loss = spending more than you store over time. Low-to-moderate exercise (aerobic system) and a calorie deficit lower insulin and raise fat mobilisation; muscle mass raises the 'salary' you burn at rest. This is why fat-loss stacks target insulin sensitivity, fat mobilisation (e.g. caffeine, carnitine) and appetite.
Key hormones: Insulin (store, blocks burning), Adrenaline/noradrenaline (mobilise fat), Glucagon, cortisol, growth hormone (mobilise fat), Leptin (satiety), Ghrelin (hunger)