Such terms as calories and nutrition reflect particularities of food metabolism. The energy contained in foods is measured in calories. The notions of calories and nutrition refer to food transformations into cell constituents and body supply with energy for various kinds of activities. Study of calories and nutrition helps achieving optimal health together with reducing the risk of some diseases. Calories and nutrition cover such topics as energy production, essential nutrients, and healthy diets. Health problems originating from shortage or excess of calories and nutrition may result in nutritional diseases.
Calories and nutrition in action
The body draws the energy from foods. The energy expressed in calories and nutrition activities are transformed into muscle work, secretion, maintenance of structural constituents and vital functions. Calories and nutrition result in the production of heat that maintains the body temperature within a normal range. Foods as the source of calories and nutrition are necessary for producing new body materials and providing energy for biochemical reactions. Carbohydrate, fat, and protein are interchangeable resources of calories and nutrition.
Value of calories and nutrition
The energy in the form of calories and nutrition value of foods are determined by means of measuring the heat output in the calorimeter. Carbohydrate gives 4 calories per gram; protein contains 4 calories per gram; and fat releases 9 calories per gram. Alcohol in beverages gives 7 calories per gram. Vitamins, minerals, and water do not possess any energy value. From 12 % to 15 % of energy comes from protein, fat gives 30 % to 40 % of energy, from 50 % to 60 % of energy is of carbohydrate origin. The body is amazingly flexible to various diets. However, dietary particularities must be taken into consideration from the standpoint of health. The energy contained in foods can be assessed. To determine the energy value of food it is necessary to know the contents of carbohydrate, fat, protein, and alcohol. Food tables and food labels offer useful information for calculating calories and nutrition intake. Foods are often a mixture of nutrients that provide energy and vitamins, minerals, and water.
Expenditure of calories and nutrition
Energy is required even if the body is at rest. From 50 % to 80 % of energy is consumed for maintenance of basal metabolism. Basal metabolism supports normal temperature, breathing, blood circulation, physiological and biosynthetic processes. Food digestion also requires calories and nutrition. Metabolic changes presuppose energy expenditures as well. Physical activity takes from 20 % to 40 % of the total energy. At rest such organs as the brain, heart, liver, and kidney demonstrate the highest metabolism. Basal metabolic activity also depends on age, sex, body temperature, and levels of thyroid hormones.