Which byproduct is associated with using fats as energy sources and is described as dangerous?

• A. Lactic acid
• B. Ammonia
• C. Urea
• D. Ketones

Answer: (D)

When fats are used for energy, the liver converts fatty acids into ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone). These ketones can power tissues when glucose is scarce, but if they accumulate faster than they’re used or excreted—as in prolonged fasting, starvation, or uncontrolled diabetes—they cause metabolic acidosis, which is dangerous. This is distinct from lactic acid, which comes from anaerobic glycolysis during low-oxygen situations or intense exercise; ammonia and urea come from protein metabolism and nitrogen processing, not fat energy pathways. So the byproduct linked to fat-derived energy that can be dangerous is the ketones.