By ingesting more calories than those spent in daily activities, the tendency is for the excess to be stored as fat by the body. But be careful: calorie – or kilocalorie – is not a substance that comes inside food, but a unit of energy measurement. The caloric value of a food serves, therefore, to indicate how much energy it provides for the body. A human being needs to consume every day, on average, 30 calories per kilogram of body weight. If a person eats more calories than that, the body stores them as fat. By ingesting fewer calories, the body loses weight, burning these reserves to meet the daily need for energy.
1. Food contains three types of nutrients: carbohydrates (common in bread and pasta), protein (abundant in meat) and triglycerides (oil and fat). At the end of digestion, food is broken down into glucose (from carbohydrates), amino acids (which form proteins) and fatty acids (from triglycerides)
2. The small intestine absorbs nutrients to release them into the bloodstream. Upon entering the liver, triglycerides revert to fatty acids. Inside, they are reprocessed to form lipoproteins that return to the blood to supply cells throughout the body.
3. If triglycerides are left over, they are absorbed by the adipose tissue – made up of 30 billion cells that store fat – through lipoproteins. This tissue appears under the skin (subcutaneous fat), around organs (visceral fat), in bone marrow, and in breast tissue.
4. Glucose, the body’s main source of energy, is used by cells or stored as glycogen in the liver and muscles. If ingested in excess, however, it can be processed by the liver to generate more triglycerides, which will be stored, that is, fat. Subcutaneous fat accumulates in thighs, hips and arms. The visceral – which increases the risk of cardiovascular disease – is stored in the belly
5. Amino acids travel through the bloodstream and are used by cells throughout the body to synthesize proteins and use them to rebuild various structures such as muscle tissue. The excess is eliminated by the kidneys in the form of urea in the urine.
CONSULTANCY: Jacob Faintuch, general practitioner at Hospital das Clínicas (SP); Rosana Radominski, president of the Obesity Department of the Brazilian Society of Endocrinology and Metabolism; and Silvia Bertoncello, endocrinologist at Hospital São Camilo (SP).