What does catabolism mean?
Catabolism refers to the series of chemical reactions within living organisms that break down complex molecules — such as proteins, fats, and carbohydrates — into simpler compounds, releasing energy that cells use to function. It is one half of metabolism, the other half being anabolism, which builds complex molecules from simpler ones and requires energy rather than producing it. Digestion, the conversion of glycogen into glucose, and the breakdown of muscle protein during fasting or severe illness are all examples of catabolic processes. In medicine and sports science the term appears frequently in phrases like 'protein catabolism' or 'muscle catabolism', where excessive breakdown can signal disease or overtraining. Derived from the Greek katabolē, meaning 'a throwing down', the word entered scientific English in the nineteenth century alongside its counterpart anabolism. Though technical, it remains useful shorthand for describing how the body dismantles matter to power itself.
nounThe set of metabolic processes in living organisms that break down complex molecules into simpler ones, releasing energy in the process.
- The metabolic breakdown of complex substances into simpler ones, releasing energy (biochemistry and physiology).
- By extension, any destructive breakdown or wasting away of tissue in the body.
"During prolonged fasting, the body shifts into a state of heightened protein catabolism to meet its energy needs."
"Exercise increases both catabolism of stored glycogen and the subsequent rebuilding of muscle tissue."
"In illness, elevated catabolism can cause rapid weight loss even when the patient eats regularly."
Rarely pluralized; the word is almost always used as an uncountable mass noun referring to a class of biochemical processes.
"Researchers compared the distinct catabolisms of carbohydrate and fat under fasting conditions."
Every time you fast, your body literally begins eating itself — that's catabolism breaking down your own muscle for fuel.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of catabolism
Catabolism derives from the Greek katabolē, meaning 'a throwing down', formed from kata- ('down') and ballein ('to throw'). The term was coined in the nineteenth century as part of the modern vocabulary of biochemistry, paired deliberately with 'anabolism', from ana- ('up'), to describe the two complementary directions of metabolism. Its Greek prefix kata- also appears in words such as cataclysm, catalog, and catalyst, all sharing the sense of something done downward or thoroughly.
Related word forms
How catabolism is actually used
A technical term used chiefly in biochemistry, physiology, medicine, and fitness writing. It carries no strong connotation in itself, though in fitness contexts it is often framed as something to be minimized (to preserve muscle), while medically it simply describes a necessary phase of energy production. The adjective form 'catabolic' is more common in casual fitness usage than the noun.
Easily confused with catabolism
Anabolism is the opposite process: it builds complex molecules from simpler ones and consumes energy, whereas catabolism breaks molecules down and releases it.
Metabolism is the sum total of all chemical processes in the body, encompassing both catabolism (breakdown) and anabolism (build-up).