Energy is fuel for the body, it enables the body to function, renew, grow and repair. We get our energy from the macronutrients (proteins, carbohydrates and fats) found in the food that we eat. The energy we put in to the body needs to be equal to the energy we expend, this leads to a healthy balance. This energy expenditure includes the basal metabolic rate (See below for further definition), growth, physical activity and thermogenesis (heat produced by the body from metabolising food eaten). An energy imbalance occurs when an excess of energy, from food and alcohol, is consumed. The liver converts energy into fat which is stored in adipose tissue under the skin. With prolonged imblances in the diet the excesses can lead to health concerns such as obesity, coronary heart disease and cancer. Energy imbalance can work in the other direction, a deficiency in the amount of energy needed by the body uses up stores of fat and glycogen leading to other health concern such as malnourishment.
Basal Metabolic Rate
The BMR shows the amount of energy a body needs to carry out the involuntary actions that keep us alive. These actions include: respiration, heart beat, brain activity, regulating body temperature, enzymes secretion, hormone and tissue production. It is measured in clinical conditions with a person being completely relaxed at about 12 hours after eating and shows about 70% of a person’s energy usage. BMR is expressed in kilojoules or calories. It is affected by a number of factors which include; body weight, gender, age, diseases, climate, activity level and pregnancy.