黑色字体是原文献
红色字体是机翻
蓝色字体是人肉翻，校对，讲解，注释，批注，说明。。。等等
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Starvation in Man
G. F. CAHILL JR
In creatures in whom mobility plays an important role in survival, the five
to tenfold greater efficiency of storage of excess calories as fat instead of
protein or carbohydrate is crucial. This is particularly true for terrestrial and
avian species who must struggle continuously against gravity. Thus in man,
who once survived as a hunter and gatherer, and in whom mobility also
played an important role in his competition with other creatures and,
unfortunately, frequently against fellow man, storage of calories as triglyceride in adipose tissue was mandatory for survival. Thus, as discussed
elsewhere in this issue, as man eats, the first priority is to provide fuel for
immediate metabolic requirements. The second is to expand his modest
glycogen reserves in liver and muscle and also to replace the amount of
protein broken down in various tissues since the last meal, particularly in
muscle. The third priority is to convert the excess, . the originally ingested
calories as carbohydrate, protein or fat, into triglyceride and to store the
calories in adipose tissue.
In fasting, the priorities are reversed. The body undergoes a series of
hormonal and metabolic changes to draw selectively on its extensive supply of
calories in adipose tissue, and to spare the breakdown of vitally needed
proteins, such as those involved in muscle contractility or in enzymes in
critical structures such as heart or liver, or, even more important, proteins
involved in nervous tissues, particularly brain, which appear not to be
mobilised at all during starvation. This chapter will discuss these various
adaptations to a deficit caloric economy, and will describe how the human
body progressively and preferentially uses fat for energy.
ENERGY STORES
First, an overall account of calories in various forms and tissues is necessary
to provide perspective to fuel economy and mobilisation in man (Table 1). A
normal adult uses 1 to Cal/min to maintain basal energy needs, or 1500 to
1800 Cal/day. With standard physical activity or in a cold environment, this
is doubled, and with strong physical activity, daily expenditures may increase
to 5000 to 6000 Cal/day. Thus the 100000 to 150000 Calories in the 12 to 16
kg of triglyceride in fat provides one to three months of survival fuel
Clinics in Endocrinology and Metabolism -- Vol. 5, No. 2, July 1976. 397
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