In the human body, fats, in addition to other functions, serve as an energy reserve to obtain the fuel the body needs in situations of high energy demand. This process, popularly known as fat burning, is called lipolysis.
Function of fats
Fats, or lipids, serve several vital functions in the human body:
- Energy Source:Fats are one of the main sources of energy, providing more than twice as much energy per gram compared to carbohydrates and proteins.
- Energy Storage:Fats are stored in adipose tissue and serve as energy when there is a low availability of other nutrients. Adipose tissue is made up of adipocytes, which are cells specialized in storing energy in the form of fat.
- Thermal Insulation:Subcutaneous adipose tissue acts as an insulator that helps maintain body temperature.
- Organ Protection:Fats surround and protect vital organs such as the heart and kidneys, cushioning them from shocks.
- Structural Component:Fats are essential in the structure of cell membranes, helping to maintain the integrity and fluidity of cells.
What is fat burning and when does lipolysis occur?
In situations of energy demand, the organism mobilizes its energy reserves through a process known as lipolysis. Fasting, carbohydrate deficiency, stress, exposure to cold or intense physical activity can lead to such a demand situation.
The lipolysis is the process by which the body breaks down stored fats (triglycerides) in adipocytes for energy. This process releases fatty acids and glycerol into the bloodstream, which can then be used by the body's cells as fuel, especially in the muscles and liver.
Lipolysis begins when hormones such as adrenaline, noradrenaline, glucagon and growth hormone bind to specific receptors on the surface of adipocytes. These hormones are released in situations of high energy demand, such as exercise or fasting. This process triggers a signaling cascade which involves the activation of the G proteinwhich activates the enzyme adenylate cyclase in the cell membrane.
Adenylate cyclase converts ATP into Cyclic AMP (cAMP) which activates an enzyme called protein kinase A (PKA). PKA phosphorylates and activates several lipases (enzymes that break down fats) that are responsible for the breakdown of triglycerides into 3 fatty acid molecules and 1 glycerol molecule.
The fatty acids released during lipolysis enter the bloodstream for further processing within the cells by a process known as beta-oxidation.
