Energy is needed for our bodies to function. It is the capacity to perform work. There are many forms of energy;
- Heat energy
- Mechanical energy
- Chemical energy
- Electrical energy
Energy can be stored, released, moved, or transformed from one form of energy to another. We get our energy mainly from the food we eat. Glucose and fatty acids in foods are the main fuels we get. Energy is captured in ATP molecules.
- 1 g of carbohydrate in food provides 4kcal.
- 1 g of protein in food provides 4kcal
- 1 g of fat in food provides 7kcal
- 1 g of alcohol we consume provided 7kcal
When the amount of energy we spent equals to the amount of energy we consume from food, we can maintain our body weight. But when we consume excess energy through food, our body stores energy as fat and we become obese or overweight.
Energy is spent to carry out the following activities;
- Basal and resting metabolism
- Physical activity
- Thermic effect of food
- Non Exercise activity thermogenesis (NEAT)
About 60% -70% of the body’s energy is spent on metabolism, 15% – 30% on physical activity, and 10% on heat production in the body.
Basal Metabolic Rate (BMR)
BMR is the amount of energy needed to maintain basic physiological functions when we are at rest after 12 hours of fasting. About 2/3 of energy expenditure is for BMR. BMR is measured after 12 hours fast while the person is resting physically and mentally, and maintain in a thermoneutral, quiet environment.
Resting Metabolic Rate (RMR)
RMR is greater than BMR. It is measured in non fating state.
Thermic effect of meal
When we eat a meal it takes about 10% of calorie content to digest, metabolize, convert and store ingested macronutrients.
Other energy expenditure
- Adaptive thermogenesis- exposure to reduced temperature, fever and other pathological conditions.
- Thermogenic effect of foods ad beverages, (Eg: Nicotine, caffein, capsaicin)
Energy for physical activity
Energy needed for physical activities is greater than the basal energy need. Calories needed for physical activities depends on;
- The type of activity
- Weight of the person
The amount of energy the body needs per day varies from person to person. It varies depending on the person’s weight, age, gender, height, fat mass, fat-free mass, genetic, thyroid function, and amount of physical activity. There are a number of other factors that contribute to this. These include muscle mass, body fat, fasting, body growth rate, genetic, hormonal and neural activity, ambient temperature, infections or diseases, medications, and nutritional deficiencies.
A calorie is a unit used to measure energy. If you want to lose weight, you need to get less energy than your body expends every day.