Macronutrients are broken down in the digestive system and transported into the bloodstream, where they are delivered to cells and used for energy. Each of the different macronutrients produces different amounts of energy. Fats yield 9 Calories per gram. Each macronutrient plays a role in promoting health. Proteins and fats are essential to provide amino-acid building blocks for body proteins and to build, maintain and repair tissues.
Carbohydrates are a necessary energy source found in vegetable and grain products.
Nutritionists, dieticians and doctors agree that people must consume a variety of foods to fulfill their daily caloric requirements. The work of the scientists seen in this episode suggests that overeating may accelerate aging. Physician and longevity researcher Roy Walford has followed a calorie-restricted but nutrient rich diet for many years. Geriatric investigator Richard Weindruch is studying effects of CR in rhesus monkeys and rodents. The research animals receive essential nutrients, but their calories are limited.