The Malnourished Patient: Nutritional Assessment and Management

Endogenous energy stores are continuously oxidized for fuel . Triglyceride present in adipose tissue is the major fuel reserve in the body and is critical for survival during periods of starvation (Table 15-1) . The high energy density and hydrophobic nature of triglycerides make it a fivefold better fuel per unit mass than glycogen . Triglycerides liberate 9 .3 kcal/g when oxidized and are compactly stored as an oil inside the fat cell, accounting for 85% of adipocyte weight . In comparison, glycogen produces only 4 .1 kcal/g on oxidation and is stored intracellularly as a gel, containing approximately 2 g of water for every gram of glycogen . Adipose tissue is unable to provide fuel for certain tissues, such as bone marrow, erythrocytes, leukocytes, renal medulla, eye tissues, and peripheral nerves, which cannot oxidize lipids and require glucose for their energy supply . During endurance exercise, glycogen and triglycerides present within muscle tissue provide an important source of fuel for working muscles .' Energy Metabolism