A weight-loss plan developed by cardiologist Robert Atkins that restricts carbohydrate drastically while allowing generous protein and fat. The induction phase limits carbs to a ketogenic minimum, shifting the body to burn fat and produce ketones, with gradual carb reintroduction in later phases. It was among the first diets to challenge the low-fat orthodoxy, and trials show it produces faster short-term weight loss than low-fat diets, though long-term differences narrow. Critics raise concerns about saturated fat intake, fiber shortfalls, and sustainability, while supporters credit its appetite-suppressing effect and metabolic improvements. Its cultural impact exceeds its nutritional nuance: Atkins made low-carbohydrate eating a mass movement and forced nutrition science to take carbohydrate restriction seriously as a research question.