Caloric requirement

Most CF patients have an increased caloric need due to increased energy expenditure through increased work of breathing and increased basal metabolism. Prevention of malnutrition requires early nutritional intervention. In patients with mild lung disease and well-controlled absorption, required caloric intake is approximately 100% to 120% of the recommended daily allowance (RDA) for age.15 As lung disease progresses, caloric requirements increase. 

Enteral nutrition is recommended in septic patients to meet the increased energy and protein requirements. Protein requirements are increased to 1.5 to 2.5 g/kg per day. Nonprotein caloric requirements range from 25 to 40 keal/kg per day.24... 

The basal diet was a measured, laboratory controlled diet based on ordinary foods fed in sufficient quantities to meet caloric requirements of the 127 subjects for weight maintenance and meeting or exceeding the National Research Council Daily Recommended Nutrient Intakes. 

Since ferrets eat only their caloric requirements, and since their gastrointestinal transit time is short (3-5 h), it is recommended that they receive diet ad libitum. Dry cat food was previously recommended for ferrets however, there are now at least two standardized ferret chows commercially available. The most important dietary variable is the quality of the protein, and ferrets appear to do best with a high percentage of animal protein in their diet (Morton and Morton, 1985). Feed consumption will be higher in the fall and winter and lower in the spring and... 

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. 

The most important biological function of carbohydrates is to provide energy. Most current dietary recommendations suggest that about 55% of total caloric requirements be provided by carbohydrates. 

A is a calculated adjustment factor allowing for the differences in caloric requirement. 

To correct for differences in body size between humans and experimental animals, three measures of body size are used in practice as the basis for the extrapolation body weight, body surface area, and caloric requirement (Eeron et al. 1990, Vermeire et al. 1999, KEMl 2003). 

The reasons for using these three measures and the advantages and disadvantages of their use have been described by Davidson et al. (1986) and Vocci and Farber (1988). In these papers, it is also explained why the body weight can be used in aU three cases. However, the body weight should be taken to the power of 1, 0.67, and 0.75 for the body weight approach, the body surface area approach, and the caloric requirement approach, respectively. These figures indicate that the approach used to correct for differences in body size will clearly affect the value of the NOAEL adjusted to the body size of humans. 

S.3.2.3 Adjustment for Differences in Body Size Caloric Requirement Approach... 

The caloric requirement, or metabolic rate approach, has also been proposed as an alternative to correction for differences in body size based on body weight. 

Feron et al. (1990) have concluded that, in general, adjustment for differences in body size between experimental animals and humans should be based on caloric requirement (energy metabolism) as this was considered to be both scientifically sound and of practical significance. 

The allometric equation relating the caloric requirement (CR) to the body weight (W) is as follows ... 

When correction for differences in body size is based on caloric requirement, the exponent n in the allometric equation is thus 3/4, or 0.75, and the human dose Xhuman (expressed in mg) can be calculated as follows ... 

Scaling Factors for Adjusting the Dose Expressed Per Unit Body Weight to the Dose Expressed Per Unit Caloric Requirement Taking... 

As mentioned earlier, the interspecies differences can be divided into differences in metabolic size (Section 5.3.2) and remaining species-specific differences. The average sensitivity of humans to the adverse effects of chemicals (after scaling for caloric requirement) is comparable to that of other species (KEMI 2003). However, an extra assessment factor is needed to account for the remaining... 

Eor the purpose of assessing the remaining interspecies uncertainty, Vermeire et al. (1999) collected and analyzed data for 184 chemicals tested in different species and via different exposure routes. NOAELs were selected from studies with mice, rats, and dogs exposed to the same chemical via the same exposure route and with the same duration of exposure. Two categories of exposure duration were defined, subacute and (sub)chronic, in order to increase the comparability of the different studies. The definition of these exposure categories is species specific, partly depending on their maximum lifetime. Subacute exposure was defined as 21-50 days for the mouse and rat, and as 28-90 days for the dog (sub)chronic exposure was defined as 90-730 days for the mouse and rat, and as 365-730 days for the dog. The oral NOAELs were adjusted to account for differences in metabolic size, i.e., by the caloric requirement approach (Section 5.3.2.3). 

In the following text, various studies will be described, which attempt to establish a scientific rationale for the selection of the interspecies assessment factor. Based on these studies, it can be concluded that a species-specific default factor based on differences in caloric requirement (see Table 5.4) should be used for interspecies extrapolation regarding metabolic size. The remaining interspecies differences should preferentially be described probabilistically, or a deterministic default factor of 2.5 could be used for extrapolation of data from rat studies to the human situation. 

Feron et al. (1990) concluded that the sensitivity of humans to chemicals is probably not very different from that of other mammals, and that a systematic error is made by carrying out extrapolation by using the body weight approach. For metabolizable compounds, the authors strongly recommended a procedure that takes the metabolic rate into account (1F° ) for scaling across species, i.e., dose correction for differences in body size between experimental animals and humans by the caloric requirement approach (Section 5.3.2.3). This approach was also considered to provide a contribution to reducing the size of the traditional safety factor in a justifiable way. 

ECETOC (2003) recommended that in the absence of any substance- or species-specific mechanism or PBPK modeling (Section 4.3.6), allometric seating based on metabolic rate (W° ) (caloric requirement approach. Section 5.3.2.3) is considered to provide an appropriate default for an assessment factor for interspecies differences with respect to systemic effects. Allometric scaling was stated as being a tool for estimating interspecies differences of internal exposure or body burden and to provide indirectly information on differences in sensitivity between species. Typical scaling factors for interspecies adjustment were noted as 7 for mouse, 4 for rat, and 2 for dog however. 

For oral exposures, administered doses should be scaled from animals to humans on the basis of the caloric requirement approach (Section 5.3.2.3), i.e., body weight normalized by the 3/4 power. It is noted that the 3/4 power is consistent with current science, including empirical data that allow comparison of potencies in humans and animals, and it is also supported by analysis of the allometric variation of key physiological parameters across mammalian species. It is also noted that it is generally more appropriate at low doses, where sources of nonlinearity such as samration of enzyme activity are less likely to occur. 

Synthesis of Fatty Acids from Glucose After a person has ingested large amounts of sucrose, the glucose and fructose that exceed caloric requirements are transformed to fatty acids for triacylglycerol synthesis. This fatty acid synthesis consumes acetyl-CoA, ATP, and NADPH. How are these substances produced from glucose ... 

Be able to convert the volumes of 02 utilized or C02 produced into daily energy requirements, and determine which types of foods are being oxidized from these data know the meaning of RQ and be able to use it in caloric requirement calculations. 

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