Our body requires energy for its metabolic and physiological functions. It derives the energy from food and its macronutrient constituents, i.e. carbohydrates, fats, and proteins. The dietary energy intake from food must meet the requirements for the attainment and maintenance of optimal health, physiological function, and well-being.
The energy requirement is the amount of food energy needed to maintain body size, body composition, and a level of necessary physical activity consistent with long-term good health. The dietary energy needs cannot be considered in isolation of other nutrients in the diet, as the lack of one will influence the others. Thus, the requirements for energy must be fulfilled through the consumption of a diet that satisfies all nutrient needs.
Mitochondria are found in the cytoplasm of all eukaryotic cells, that is, the cells with clearly defined nuclei. Their primary function is to generate large quantities of energy in the form of adenosine triphosphate (ATP). The number of mitochondria per cell varies widely.
ATP, the energy-carrying molecule, is found in the cells of all living things. When ATP is broken down, energy is released and can be harnessed for cellular work. Because ATP is so easily broken and reformed, ATP is like a rechargeable battery that powers cellular processes.
ATP is often referred to as the “molecular unit of currency” of intracellular energy transfer. ATP captures energy obtained from the breakdown of the food and releases it to fuel the cellular processes. Our body regenerates and recycles its own body weight equivalent in ATP each day.
Daily energy requirements –
There are only small amounts of ATP in the body. Therefore, it is necessary to have sufficient energy stores for backup. The amount of daily energy requirement depends on an individual’s daily energy consumption and metabolic energy requirement, which depends on one’s body weight and activity level.
The energy we get from food to fuel our body, is measured in kilojoules. Fat, carbohydrate and protein, which are found in foods, all provide energy.
The basic energy consumption of the human body is 4 kJ/kilogram of body weight per daily hour. So an individual’s basic energy consumption can be calculated as follows:
Total Energy Consumption = Body weight (Kg) × 4 KJ × 24 hours/day / 4.18 kJ
The total energy consumption value is divided by 4.18 kJ in order to convert the value into kilocalories (1 kcal = 4.18 kJ). This calculation represents daily energy consumption.
Individual energy requirements vary with age, gender, body size and activity levels. Excess food intake that is not used as energy can be stored in the body as fat. Excessive fat storage can lead to a high body mass index (BMI).
BMI indicates a person’s body fat and is determined by an individual’s height and weight. In adults, the normal suggested BMI ranges between 19 and 24. A high BMI can potentially lead to illness or health complications. In order to have an ideal BMI, an individual’s energy intake must not exceed the energy burned on a regular basis.
Energy balance –
Energy balance is the relationship between calories taken into the body through food and drink and calories being used in the body for our daily energy requirements.
When you take in more calories than you consume, you are in a positive energy balance. When you take in fewer calories than you consume, you are in a negative energy balance. You energy balance affects your metabolism, hormonal balance, and mood.
A negative energy balance leads to weight loss. The body detects an energy deficit and fat reserves are called upon to make up the difference. A positive energy balance has its own ramifications not only in terms of weight gain but also in terms of health and fitness.