Health and Fitness Hints

The body’s energy needs are met by nutrients in food. This is represented by the energy intake model- number of kcal or kjoules eaten each day. Output on the other side is the energy the body uses for four general purposes: basal metabolism, physical activity, thermic effect of food or TEF and nonexercise activity thermogenesis or NEAT- a minor form of energy turned into heat production.

Basal metabolism is the minimum expenditure to keep a resting, awake body alive in a warm environment during a fasting state of 12 hours. The process includes respiration, heart beat, and other functions but not include energy used for digestion or physical activity. Generally basal metabolism is higher in individuals with large amounts of lean body mass than those with large proportion of fat mass. Tissues with high metabolic activity and high energy needs at rest are the brain, kidneys, muscles and liver. Basal metabolism requires about 70% of total energy use by the body.

Other factors that control basal metabolism include:
• Gender-males because of greater lean body mass average higher energy use.
• Body surface area- the greater the area the greater the body’s heat loss.
• Age- nutritional needs and metabolism rates of preschool children are different to those of a middle age individuals; as we age basal metabolism rate falls.
• Pregnancy- increases basal metabolism
• Nutritional state- in the sort term a low intake of nutrients will lower the basal metabolism rate by up to 20%.
• Norepinephrine and thyroid hormones - increase basal metabolism.
• Smoking and caffeine- increase basal metabolism.

Physical activity increases energy needs well beyond that of basal needs. It is your choice to be active or inactive. However, this choice, amount of nutrition and physical activity, will determine your total energy expenditure each and every day. Based on statistics people living in western societies eat more and are less active. They seek less physical activity and more leisure time. Such a behavior has led in the alarmingly results of a vertical increase in numbers of obesity and numerous health problems related to excess daily consumption of nutrients.

Thermic Effect of Food, in addition to basal metabolism and physical activity, energy is used in digestion, absorption and in processing of food nutrients. This type of expenditure is equivalent to about 10% of the total energy received from food nutrients. Large intake of nutrients in one sitting will show a higher TEF than if the same amount nutrients was consumed over several hours.

Nonexercise Activity Thermogenesis corresponds to nonvoluntary activity as a result of overeating. The increased intake of food may lead in to twitching and wriggling due to sympathetic nervous system activity and maintenance of muscle tone. In general a sedentary individual uses up to 80% of energy for basal metabolism and TEF. The rest is used for physical activity and nonexercise activity thermogenesis.

The amount of energy intake needs from the consumption of nutrients and the amount of energy output-daily physical activities etc., can be both measured by calorimetry or just estimated based on age, physical activity, height and weight.

nutrients energy and metabolism

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