What is lipolysis?
Lipolysis is the breakdown of triglycerides in adipose tissue into free fatty acids and glycerol for use as energy. It is regulated by hormones including catecholamines (epinephrine, norepinephrine) and inhibited mainly by insulin.
Key Points
- •Cortisol timing — cortisol follows a daily rhythm (highest after waking); how its timing affects fat use day to day is not well established
- •Insulin — high insulin suppresses lipolysis; fasting and low-carb states promote it
- •Sleep — deep sleep supports growth hormone release, which favors fat mobilization
Why does Lipolysis matter?
Lipolysis matters because it is how the body unlocks stored fat for energy. Fat is kept mainly as triglycerides in fat cells, and lipolysis splits them into glycerol and free fatty acids that muscles, the heart, and other tissues can use.
This process is essential between meals, overnight, during fasting, and during prolonged exercise. The released glycerol can also be used by the liver to make glucose. Releasing fatty acids is only the first step, though; burning fat depends on whether tissues actually take up and oxidize them.
What affects Lipolysis?
Hormones are the main regulators. Insulin strongly suppresses lipolysis, which is why it slows after meals, especially carbohydrate-rich ones. Adrenaline, noradrenaline, glucagon, growth hormone, and cortisol generally promote it, particularly during fasting, stress, and exercise.
Other influences include time since the last meal, exercise intensity and duration, sleep, and overall energy balance. Rates also differ between fat depots. When lipolysis is chronically elevated, as in insulin resistance, excess free fatty acids in the blood may contribute to metabolic problems, including fat buildup in the liver.
In ONDA Life
The CHM article explains why no consumer wearable measures cortisol, and why claims that evening cortisol "blocks" fat burning are not supported.