rasvanpolton

Rasvanpolton is the metabolic process by which fatty acids are oxidized to produce energy in cells. It is a major source of cellular ATP during rest and prolonged, lower-intensity exercise, and it contributes to energy production during many fasting or caloric deficit states. The process begins with lipolysis, where triglycerides stored in adipose tissue are broken down by hormone-sensitive lipase into free fatty acids and glycerol. Circulating free fatty acids bind to albumin and are taken up by tissues such as muscle. Inside mitochondria, fatty acids are activated and transported via the carnitine shuttle, then subjected to beta-oxidation, producing acetyl-CoA, NADH, and FADH2. Acetyl-CoA enters the citric acid cycle, while NADH and FADH2 donate electrons to the electron transport chain, yielding ATP, CO2, and water. The relative contribution of fat oxidation depends on intensity and duration of activity, as well as hormonal and nutritional state. The respiratory exchange ratio (RER) is around 0.7 when fat is the primary fuel, and approaches 1.0 when carbohydrate oxidation predominates.

Regulation is influenced by insulin (which suppresses lipolysis) and catecholamines (which promote it), as well as cortisol and growth hormone. Endurance training and higher mitochondrial density increase the capacity to oxidize fats, while carbohydrate availability modulates the balance between fat and carbohydrate usage. In weight management, fat loss depends on overall energy deficit; maximizing fat oxidation can be beneficial for endurance performance but does not guarantee fat loss by itself.