What occurs when there is an excess of acetyl CoA in the body?

When there is an excess of acetyl CoA in the body, the most significant outcome is the formation of ketone bodies. This process occurs primarily in the liver when carbohydrate intake is low, such as during fasting, prolonged exercise, or a low-carbohydrate diet. Under such conditions, the body needs an alternative energy source, and the surplus acetyl CoA, derived notably from fatty acid oxidation, is converted into ketone bodies (including acetoacetate and beta-hydroxybutyrate). These ketone bodies can then be utilized by various tissues, including the brain, as an energy source when glucose availability is limited.

While other metabolic processes such as the formation of fatty acids can occur when there is sufficient energy or carbohydrates available, the shift to ketogenesis is a primary metabolic response to high levels of acetyl CoA under specific conditions where carbohydrate intake is restricted. The formation of glucose and amino acids is less directly related to excess acetyl CoA; gluconeogenesis, the process of producing glucose, typically requires substrates such as lactate or amino acids rather than acetyl CoA.