The Different Categories of Metabolic Activity

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cold environments the TDEE can increase. Pregnancy and breastfeeding increases the TDEE due to the extra energy necessary to develop and nurture an offspring, a breastfeeding mother may expend extra 425 to 700 calories a day (Scacia, 2005). With the gross energy expenditure, which is the energy necessary to perform and recover from a physical activity, we can calculate the net energy expenditure, which is the difference from the energy expended to perform an activity and the energy to recovery from it.

The value of the TDEE is the amount of calories needed per day to keep a person’s current weight, so by limiting the daily intake of calories below this value would decrease a person’s TBM, and by increasing the TDEE a person would gain weight. The total daily energy expenditure can be used to reach fitness goals, such as lose weight, gain muscle, or improve sports performance, while the resting daily energy expenditure (RDEE) measurement seems to have a more clinical significance.

The resting daily energy expenditure (RDEE) is the amount of energy required by the body to keep its functions during a 24 hours period in a resting state. There are many mathematical formulas to estimate the RDEE, the most used is the Harris Benedict’s equations, which have been found to overestimate the values by 6-15% compared to the calorimetry method. The calorimeter measures the amount of heat produced by body mass; it is an expensive and impractical method to be used in a clinical setting, so an easier way to measure the RDEE is by analysis of the respired gases by a metabolic cart (Schwartz, 1998).

The RDEE is a useful tool to prevent over or underfeeding of individuals, especially in a clinical setting. Malnutrition can lead to reduced respiratory muscle strength, slower healing processes, infection, and overall impaired metabolism. In the case of overfeeding, the energy not used by the body can be stored as fat, increasing the work of breading which may increase CO2 concentration. RDEE values may help in the process of weaning ventilators patients to resume to normal breathing (Saha, 2015).

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