How Do Thermogenic Fat Burners Work?


Thermogenic fat burners are dietary supplements that stimulate your sympathetic nervous system to raise the metabolic rate, increase energy expenditure and burn body fat. Thermogenics are often referred to as ECA stacks. ECA stands for Ephedrine, Caffeine, and Aspirin. Nowadays, Aspirin is hardly ever used and Ephedrine has been banned by the Food and Drug Administration because of serious side effects, which included increased blood pressure, irregular heart rate, strokes and heart attacks.

What are the main components of fat burners today? They are caffeine or its herbal counterparts (guarana, kola, yerba mate) and epinephrine/adrenaline replacements (for example, synephrine). Thermogenic supplements may also contain epigallocatechin gallate (EGCG) and capsaicin.


Caffeine is a chemical compound found in most weight-loss supplements. It helps to suppress appetite and increase metabolism. It is also an efficient diuretic and water loss is still weight loss when you are on a scale. However, caffeine is not a magic substance allowing you to burn fat easily. It increases the metabolic rate by 4-5 per cent only and not for long. What is good about caffeine is that it can give you a slight nudge of energy allowing you to work out harder or jog longer. In small amounts, caffeine is safe for most people; in large doses it causes tremors, agitation, and irregular heart rate.


Synephrine is usually included in fat burning supplements as bitter orange (Citrus aurantium). Synephrine is on the NCAA (National Collegiate Athletic Association) banned drug list. Synephrine increases heart rate, squeezes blood vessels and causes high blood pressure. It was not proven that Synephrine is safer than Ephedra.

Epigallocatechin gallate

EGCG (Epigallocatechin gallate) is an antioxidant found in green tea (but not in black tea). EGCG helps to increase fat oxidation and may augment weight loss.


Capsaicin is an antioxidant found in spicy peppers. It has a modest effect on increasing metabolism, similar to the effect of caffeine or green tea. Capsaicin also helps to suppress hunger and can help in reducing calorie intake.


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