Adult human body has to have, because of every day fluctuating energy intake and energy needs, very precious adaptive mechanisms for maintenance of heat homeostasis in the body and nearly stable body weight and body composition, which are optimal for life and reproduction. These short term functioning adaptive mechanisms are called "empty biochemical mechanisms", where chemically bound energy is transformed to heat without work performance. These mechanisms are present on the cellular level (substrates cycles, uncoupling of respiration chain), on the interorgan metabolic level (glycolysis and gluconeogenesis between liver and adipose tissue-glucose-lactate cycle). Central nervous system controls them via many factors; the most important are catecholamines, leptin, insulin, thyroid hormones, cortisol, growth and sex hormones. Neurotransmitters and neuronal net influence energy intake and other behavior. Obesity seems to be associated with the amelioration or overcoming of possibilities of function short-term effective adaptive mechanisms.