BIOLOGICAL ENERGETICS 



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distance of (540,000 X 0.20) -:- 123, or 878 feet in order to use it com- 

 pletely. If tliis very considerable exertion, or its equivalent in other 

 work, is not made, the extra calorics provided by the snack will inevitably 

 go to form fat. 



As another example, suppose a person wishes to exercise enough to 

 remove one pound of fat. The fat tissues of the body contain about 

 one-fifth moisture and four-fifths actual fat. One pound of such tissue, 

 therefore, represents 454 X 0.8 X 9, or 4080 Cal. According to Table 

 16-5, walking at the rate of 3.75 miles per hour involves a total energy 

 expenditure of 300 Cal. per hour for a 70 kg. man. Therefore, the man 

 would have to walk 13.6 hours (4080 -=- 300) , or a distance of 51 miles 

 (13.6 X 3.75) to "burn off" the pound of fat. Of course, considerably 

 more weight might be lost in the form of perspiration, but this weight 

 would be quickly regained through increased water intake. These ex- 

 amples show that it is very difficult, and usually impractical, to counteract 

 excessive food intake by increased muscular activity. 



Another source of confusion is the fact that some individuals gain 

 weight on a food intake which would not be excessive for others. This 

 may be due to differences in the efficiency with which the food is digested 

 and absorbed, or to differences in basal energy requirements. Other 

 things being equal, older people need fewer calories than younger ones, 

 and a short stocky person probably has a lower basal metabolism than 

 a tall gangling one. 



The solution to the problem of overweight is very simple in theory, 

 but, of course, in practice it is complicated by the appetite, which unfor- 

 tunately is not an accurate guide to the energy requirements of the body. 

 However, only a slight reduction of the calorie intake, if persistently 

 continued, is capable of restoring normal weight. If as calculated above, 

 one pound of fatty tissue corresponds to 4080 Cal., a reduction of only 

 100 Cal. a day would amount to the equivalent of 8 pounds a year. Ad- 

 justments of this magnitude can usually be made merely by intelligent 

 food selection. The principles to be observed are to avoid fat insofar 

 as possible and to increase the consumption of high protein foods such 

 as fish, poultry, and lean meat. A high protein intake satisfies hunger 

 with the consumption of relatively few calories. Bulky foods like fresh 

 vegetables are also indicated. Severe dieting or use of drugs for reducing 

 are at best undesirable and often actually dangerous to health. The most 

 satisfactory procedure is a rearrangement of one's eating habits such that 

 a gradual but steady weight reduction occurs. 



REVIEW QUESTIONS ON BIOLOGICAL ENERGETICS 



1. What is a calorie; a foot-pound? How many feet would a 150 lb. weight have 

 to be raised to use up energy equivalent to 500 calories? 



2. If the heat of combustion of ethyl alcohol is 326 Cal., how many calories would 



