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Abstract

Both humans and animals have used much energy when they move, work and continue activities. 1 This energy is from the tricarboxylic acid (TCA) cycle which is well-known for years. 2 It is also called as citric acid cycle (CAC) or Krebs cycle. 3 It can produce much energy by the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. 4 Among them, carbohydrates axis seemed to be the main route for energy production in usual basic and clinical education and biochemistry in the medical school. However, there is a possible perspective that glucose had not made a central role.Human beings in ancient times had showed evolutionary changes of metabolic programs. 1 There were two situations for human nutritional circumstances. One was fasting which was common about 4-7million years. Due to food deprivation, elevated ketone bodies had main energy-producing system. Another was overeating which has been found in recent decades. Due to food abundance, people have gradually taken much refined cereals of carbohydrates. 5 Consequently, insulin resistance has been elevated, which has brought non-communicable diseases (NCDs) such as diabetes, obesity and metabolic syndrome. 6 These changes caused social and medical problems in the world. 5