Does ketone body formation increase or decrease when insulin is released?

When insulin is released, the formation of ketone bodies decreases. Insulin plays a crucial role in the regulation of carbohydrate and fat metabolism. In the presence of insulin, there is an increase in the uptake of glucose by cells, which becomes the preferred energy source over fatty acids.

Insulin promotes the conversion of glucose into pyruvate through glycolysis and subsequently encourages the synthesis of fatty acids and their storage as triglycerides in adipose tissue. This process reduces the mobilization of fat from adipose tissues, leading to decreased availability of free fatty acids for conversion into ketone bodies in the liver.

Additionally, insulin inhibits the activity of hormone-sensitive lipase, an enzyme responsible for lipolysis—the breakdown of fat stores, which further reduces the substrate needed for ketogenesis. As a result, when insulin is released, ketone body formation is suppressed, leading to decreased concentrations of these compounds in the bloodstream. This mechanism is particularly important during the fed state when nutrients are available and energy needs are met through glucose and lipid storage rather than ketone body production.