Energy and Energy Balance

  • Douglas W. Wilmore
Part of the Reviewing Surgical Topics book series (RST)


Man is an energy machine able to convert food or body fuel stores to mechanical work. The efficiency of energy conversion to work can be calculated from the ratio of external work to internal energy conversion rate. In fed man, a small portion of heat is lost following the intake of food, and this is called the entropy or free energy of a foodstuff, indicating that part of the energy obtained from food is thermodynamically obligated for conversion to heat. This may account for 5–10% of the initial heat lost. The conversion of food energy into high-energy biochemical bonds is inefficient, and about half of the potential energy from food is dissipated as heat. Of the remaining 45% of the free-energy pool stored as ATP or other high-energy bonds, only about half is utilized for external work, which occurs only when skeletal muscles are used. The majority of high-energy substances are utilized for internal work (respiration, circulation, cell pumps, etc.), resulting in the generation of a large quantity of heat (Fig. 1.1).


Oxygen Consumption Metabolic Rate Body Surface Area Heat Production Basal Metabolic Rate 
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Copyright information

© Plenum Publishing Corporation 1977

Authors and Affiliations

  • Douglas W. Wilmore
    • 1
  1. 1.U. S. Army Institute of Surgical ResearchBrooke Army Medical CenterFort Sam HoustonUSA

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