When protein is eaten in excess, the body doesn’t store amino acids as extra protein. Instead, amino acids are deaminated in the liver, removing the nitrogen (which is then excreted as urea). The remaining carbon skeletons can be used for energy or redirected into glucose production (gluconeogenesis) or fat synthesis (lipogenesis) if energy intakes are high. That’s why the correct idea is that excess protein is broken down for energy or used to make glucose and fat. If needed, some amino acids can be reused for other nonprotein compounds, but there’s no stored “reserve” of amino acids like there is for fat or carbohydrate.

Metformin is the pharmacologic option shown to reduce progression to type 2 diabetes in adults who are at high risk. It works by improving insulin sensitivity and decreasing hepatic glucose production, which helps prevent the switch from prediabetes to overt diabetes. Evidence from major trials shows a meaningful reduction in risk, though lifestyle changes generally have a larger effect; metformin remains a practical preventive choice, especially for younger individuals, those with higher BMI, or women with a history of gestational diabetes. Insulin is used to treat diabetes, not to prevent it. Sulfonylureas stimulate insulin release and carry hypoglycemia risk, so they aren’t used for prevention, and glucagon is used for treating severe hypoglycemia, not preventing diabetes.

In parenteral nutrition, energy is provided mainly by carbohydrates because they’re readily metabolized to meet daily energy needs. A glucose (dextrose) solution is the most common base energy source in PN formulations, delivering quick, controllable calories and allowing other components—like amino acids for protein synthesis and lipids for additional energy and essential fatty acids—to be added as needed. Lipids do contribute substantial energy and essential fatty acids, but they are usually given as a separate emulsion to round out energy intake, not as the primary energy source. Amino acids supply nitrogen and building blocks for tissues, with energy contribution being secondary. Therefore, glucose solution is the typical energy-providing component in parenteral nutrition.

After fats are digested and absorbed, they are packaged into chylomicrons. In enterocytes, fatty acids and monoglycerides are reassembled into triglycerides and combined with apolipoprotein B-48 to form these lipoproteins. Chylomicrons then enter the lymphatic system via the lacteals and travel through the lymph before reaching the bloodstream, delivering triglycerides to tissues via lipoprotein lipase. The remaining chylomicron remnants are cleared by the liver. Other lipoproteins—VLDL, LDL, and HDL—are involved in transport of endogenous lipids or cholesterol, not the immediate transport of dietary fat after absorption.