Metabolic rate basal

Basal metabolic rate The rate of oxygen consumption by a person at rest. 

The basal metabolic rate for adults is 1 to 1.2 Calories/minute or 60 to 72 Calories/hour. This energy powers the movement of the chest during respiration and the beating of the heart—processes that are obviously necessary for life. However, a surprisingly large fraction of the BMR is used by cells to maintain ionic gradients between their interior and the fluid that surrnunds them (the interstitial fluid nr tissue fluid). 

Animal nutritionists have developed formulas to guide them in recommending the amount of food to feed animals in captive situations such as in zoos. First, the number of calorics needed to maintain the animal while at rest is determined—this is called the basal metabolic rate (BMR). In general, a reptile s BMR is only 15 percent that of a placental mammal, while a bird s is quite a bit higher than both a reptile s and a mammal s. For all animals, the number of calories they should receive on a maintenance diet is twice that used at the basal metabolic rate. A growing animal should receive three times the number of calories at the BMR, while an animal in the reproductive phase should receive four to six times the BMR. 

The average basal metabolic rate for humans is about 65 keal/h, or 1600 keal/day. Obviously, the rate varies for different people depending ori sex, age, weight, and physical condition. As a rule, the BMR is Jow er for older people than for younger people, is lower for females than for males, and is lower for people in good physical condition than for those who are out of shape and overweight. A BMR substantially above the expected value indicates an unusually rapid metabolism, perhaps caused by a fever or some biochemical abnormality. 

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Triiodothyronine (3, 5,3-L-triiodothyronine, T3) is a thyroid hormone. It is producedby outer ring deiodination of thyroxine (T4) in peripheral tissues. The biologic activity of T3 is 3-8 times higher than that of T4. T3 is 99.7% protein-bound and is effective in its free non-protein-bound form. The half-life of triiodothyronine is about 19 h. The daily tur nover of T3 is 75%. Triiodothyronine acts via nuclear receptor binding with subsequent induction of protein synthesis. Effects of thyroid hormones are apparent in almost all organ systems. They include effects on the basal metabolic rate and the metabolisms of proteins, lipids and carbohydrates. 

Sipilainen R, Uusitupa M, Heikkinen S, Rissanen A, Laakso M. Polymorphism of the / 3-adrenergic receptor gene affects basal metabolic rate in obese Finns. Diabetes 1997 46 77-80. 

Daily energy requirements for children are approximately 150% of basal metabolic rate with additional calories to support activity and growth (Table 57-5). Requirements increase with fever, sepsis, major surgery, trauma, burns, long-term growth failure, and chronic conditions (e.g., bronchopulmonary dysplasia, congenital heart disease, and cystic fibrosis). 

There is a decrease in basal metabolic rate with a decline in lean body mass and less physical activity. The caloric requirement may, therefore, be reduced... 

Body composition varies with age. The pediatric population has unique physiologic needs that make nutritional requirements distinctly different than adults. In children, caloric requirements per kilogram are higher because of their higher basal metabolic rate (BMR). BMR is approximately 50-55 kcal/ kg/day in infancy and declines to about 20-25 kcal/kg/day during adolescence. 

By definition all hormones affect the behavior of their target cells. Examples of the interplay between endocrine disturbances and their biochemical consequences are provided by some of the diseases of the thyroid, which directly affects basal metabolic rate, and diabetes mellitus, where glucose metabolism is deranged. 

The power required to sustain physiological processes can be calculated by using the above equation. If a pressure-volume loop for a respiratory cycle is plotted, the work of breathing may be found. If the respiratory rate is now measured then the power may be calculated. The power required for respiration is only approximately 700-1000 mW, compared with approximately 80 W needed at basal metabolic rate. 

Food intake is one side of the body weight equation energy expenditure is the other. One aspect of energy expenditure is our basal metabolic rate. That is the rate of which we consume energy when at rest. Basal metabolic rates vary significantly from person... 

Basal metabolic rate is decreased under conditions of starvation (including dieting as noted above one more reason why it is tough to lose weight) and increased under conditions of feeding. These responses tend to keep body weight constant. Thyroid hormone increases basal metabolic rate. Hyperthyroid people tend to be slender. 

Basal metabolic rate the rate of energy consumption when at rest. 

The quantitative importance of each pathway varies from one tissue to another and from one protein to another. Although hydrolysis of the peptide bonds does not involve ATP, the various processes of protein degradation require considerable expenditure of energy, possibly more than is required for protein synthesis. It is not suprising, therefore, that protein turnover contributes at least 20% to resting energy expenditure (basal metabolic rate). 

Interspecies differences (animal-to-human) mouse, a default value of 7 X 3 rat, a default value of 4 X 3 rabbit, a default value of 2.4 X 3 dog, a default value of 1.4 X 3. The first factor for each species is a calculated adjustment factor, allowing for differences in basal metabolic rate (proportional to the 0.75th power of body weight). The second factor of 3 is the assessment factor applied for remaining uncertainties (Section 5.3.3), for which the default value is 3. For local skin and respiratory tract effects, the assessment factor is 3, as adjustment for differences in body size is inappropriate. 

If physiologically based pharmacokinetic (PBPK) models cannot be used, interspecies extrapolation is best undertaken by means of scaling according to basal metabolic rate, see Section 5.3.2.3. A second aspect, interspecies variability, should be considered in cases where a higher than average level of safety (achieved by consideration of a higher percentile of the substances) is desired. 

The surface area approach has been proposed as an alternative to correction for differences in body size based on body weight. This approach is founded on the notion that the basal metabolic rate of vertebrates is a fundamental biological parameter, i.e., a final common expression of physiological and biochemical functions, which is remarkably well related to the body surface area across species and within species (Davidson et al. 1986). 

The authors noted that, in comparison with the scaling factor, the traditional 10-fold factor contains an additional extrapolation factor for possible additional toxicokinetic or toxicodynamic variability apart from the basal metabolic rate scaling. This additional factor, which can be interpreted as the traditional 10-fold factor divided by the scaling factor, ranges from approximately 1.5 for the mouse (10/7= 1.4) to approximately 6 for the rhesus monkey (10/1.6 = 6.3). The authors considered that the additional factor thus comprises levels of safety, which are currently nonuniform, and this inhomogeneity is not supported toxicologically. 

TNO has suggested a default interspecies assessment factor composed of a scaling factor allowing for differences in basal metabolic rate for oral smdies depending on the... 

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