Dietary macronutrient intake of carbohydrate, fat and protein is important for health. Each macronutrient can be further classified depending on its constituent molecules and chemical structure that results in differences in metabolism and function. For example, a monosaccharide carbohydrate will impact metabolic health differently to a polysaccharide carbohydrate. A saturated fatty acid has different bodily functions to a polyunsaturated acid. Some proteins and fatty acids are deemed ‘essential’ as they cannot be synthesised in the body and must be obtained through the diet. Understanding the chemical structure of both carbohydrates and fatty acids is essential to understanding dietary intake and impact on metabolic health. In this lesson, we look in detail at the different classifications of macronutrients, their chemical structure, function and impact on health.