Macronutrients are organic compounds that are put into our body in relatively large quantities (grams). They serve as an energy source but also have other important functions. They include proteins, fats and carbohydrates. Unlike energy nutrients, vitamins and elements (minerals), which we consume in smaller quantities (in milligrams or micrograms), they do not serve as an energy source in the body. Fats have the highest energy value. During oxidation, 1 g of fats enables 9 kcal (37 kJ) of energy and one gram of proteins 4 kcal (17 kJ), the same as one gram of carbohydrates (4 kcal (17 kJ)). One gram of alcohol generates 7 kcal (29 kJ) during oxidation, but it is not considered a nutrient due to its adverse effect on physical growth, development and regeneration. There are two parameters in nutrition that are important for assessing the nutritional value of food: energy and nutritional density. Energy density is defined as the amount of energy per gram of food or millilitre of beverage and tells us how much energy a food has per unit weight or volume. Absolute oils have the highest energy value – approximately 9 kcal/g. The recommended meal energy density for a normally fed person is from 1 to 1.5 kcal/g. If a meal contains more than 2.5 kcal/g, it may represent a risk factor for excessive weight gain and obesity because of the too-high energy intake. Fruit and vegetables have a low energy density and are thus desired in nutrition. The nutritional density of food is defined as the quantity of nutrients (in grams, milligrams or micrograms) per energy unit (per 1 MJ) and tells us the quantity of nutrients (carbohydrates, proteins, fats, vitamins or elements or other substances) that a food contains per unit of energy. Foods with a high nutritional density contain significant quantities of vitamins, elements and other biologically important substances per relatively low quantities of energy. For example, fruit and vegetables are considered high nutritional density foods, while foods containing sugar, saturated fats and alcohol are considered foods with poor nutritional value.