People are actually meant to eat meat, not both meat and plants, because of how our bodies and evolution show we're built for a meat-only diet.

Consumption of animal protein triggers gastrin release, which stimulates parietal cells to secrete hydrochloric acid, lowering gastric pH to 1–3 to denature proteins and activate pepsin for efficient proteolysis.

Low dietary carbohydrate intake reduces insulin signaling, leading to hepatic insulin resistance that promotes gluconeogenesis from amino acids to maintain blood glucose for the brain.

Reduced insulin and low glucose availability trigger lipolysis, releasing fatty acids that are transported to the liver and oxidized to produce acetyl-CoA, which exceeds TCA cycle capacity and is diverted into ketone body synthesis.

Ketone bodies—beta-hydroxybutyrate and acetoacetate—are released into circulation and used by the brain, heart, and muscles as alternative energy sources in place of glucose.

Low dietary fiber and high protein intake shift the gut microbiome from fiber-fermenting to proteolytic bacteria, which break down amino acids into branched-chain fatty acids, ammonia, and hydrogen sulfide.

Dietary carnitine and choline from meat are metabolized by gut bacteria into trimethylamine, which is oxidized in the liver to trimethylamine-N-oxide, a systemic metabolite linked to cardiovascular effects.

Reduced amylase gene copies and low salivary amylase activity limit the ability to break down starches before they reach the stomach, reflecting evolutionary adaptation to low-starch diets.

Intact meat particles larger than 2 mm are retained in the stomach by the pyloric sphincter, prolonging gastric residence time to allow complete acid and enzymatic digestion.

Beta-hydroxybutyrate enters cells and inhibits histone deacetylases, increasing histone acetylation and activating genes that enhance resistance to oxidative stress.