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6 Calories: Total Macronutrient Intake, Energy Expenditure, and Net Energy Stores
Pages 139-158

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From page 139...
... When energy expenditure exceeds energy intake, energy balance is negative and leads to weight loss. When intake equals expenditure, equilibrium results and body fat is maintained, regardless of whether the body weight is at, above, or below normal.
From page 140...
... For example, long-distance runners have high caloric intakes. More moderate levels of physical activity may increase food intake by lean but not by obese subjects.
From page 141...
... This method holds promise for resolving issues related to the stoichiometry of energy expenditure and intake in ambulatory subjects (L-ifson, 1966; Schoeller et al., 1986~. Other methods of estimating energ, expenditure include diaries of physical activity, which are widely used in epidemiologic studies, and measurement of heart rate, because it varies directly with activity level.
From page 142...
... Histoncal Trends The transition from an agricultural economy to a manufacturing economy and more recently to an information-gathering sedentary society has been associated with a steady decline in energy intake presumably because of decreased caloric expenditure. Average energy intake has been used as a surrogate measurement for energy expenditure, since it is assumed that over time, individuals are in energy balance.
From page 143...
... Measurement of body density is one of the better and most widely accepted methods for estimating total body fat and is often used as the reference standard. By determining body weight in air and under water, and correcting for lung volume, the body can be subdivided into its fat and fat-free compartments.
From page 144...
... This appears to be associated primarily with a reduction in physical activity and a corresponding reduction in lean body mass. An increase in energy intake may also be associated with this phenomenon.
From page 145...
... Under these conditions, the nearly doubled or tripled caloric intake is utilized primarily for milk synthesis to supply the lactational demands of the suckling young. At the end of lactation, despite the large increase in food intake, the body fat stores of the rat are reduced below prepregnant and prelactating levels.
From page 146...
... it has been well demonstrated in several species of normally lean animals (males, not females) that increased physical activity in the absence of increased caloric intake leads to a decrease in body weight and a change in body composition.
From page 147...
... In at least some species, alterations in body fat content clearly precede any changes in the metabolism of brown adipose tissue (Greenwood et al., 19811. In obese animals, alterations in substrate utilization lead to alterations in body composition (i.e., increased fatness and decreased lean tissue)
From page 148...
... EVIDENCE ASSOCIATING TOTAL ENERGY INTAKE WITH CHRONIC DISEASES Atherosclerotic Cardiovascular Diseases Epidem~oJog~c Studies The relationship of total energy intake tO cardiovascuiar diseases has been examined in several studies. Subjects who develop heart disease have a history of lower total caloric intake on the average compared to those who remain free of the disease (Gordon et al., 1981~.
From page 149...
... However, there is little question that when animals increase their total food intake they develop adiposity (see Animal Studies subsection of The Relationship of Caloric Intake to Body Weight and Energy Stores, above) , and adiposity is usually associated with the development of insulin resistance (Stern et al., 1975; Susini and Lavau, 19781.
From page 150...
... In most cases, weight reduction and restoration of a more normal body composition reverse the effects of increased caloric intake on insulin resistance. Thus, it becomes exceedingly difficult to identify any specific effect of calories, independent of the effects on overall adiposity, on the development of diabetes.
From page 151...
... However, animal species fed high fat diets tend to gain more weight than those fed low-fat diets, even when the caloric intake is similar. This may be because less energy is required to store dietary fats as body fat than to convert dietary carbohydrates or protein tO fat for storage (Pariza, 1987~.
From page 152...
... Clinical Studies In contrast to the epidemiologic studies, there is clear evidence from clinical studies that increasing physical activity can improve glucose tolerance and that physical inactivity can worsen it. Bjomtorp and colleagues (1973)
From page 153...
... SUMMARY Clinical and animal data indicate that increased energy intake leads to an increase in body energy stores and that reduced caloric intake lowers energy stores. In cross-sectional population studies, however, total caloric intake has no direct corre' ration with body weight and generally shows an inverse correlation with body weight.
From page 154...
... In creased physical activity may increase energy intake In lean subjects but not necessarily in over' weight people. There is no current explanation for this phenomenon.
From page 155...
... 1986. Physical activity, glucose tolerance, and diabetes mellims: the Whitehall Study.
From page 156...
... 1977. Habitual physical activity and glucose tolerance.
From page 157...
... 1981. Sympathetic control of brown adipose tissue in the regulation of body weight.
From page 158...
... 1977. Energy intake and physical activity in obese children.


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