Human Biochemistry, Volume 1 - Murray R. 1993

Bioenergetics and Metabolism of Carbohydrates and Lipids
Regulation of Lipid Metabolism and Tissue Energy Sources
Biomedical Significance

Under conditions of a positive caloric balance, a significant portion of the potential energy from food is stored as Glycogen or fat. In many Tissues—even with normal Nutrition, let alone in states of caloric deficit or starvation—Fatty acids rather than glucose are preferentially oxidized. The reason for this is the need to conserve glucose for those tissues (such as the Brain or erythrocytes) that constantly require it. Consequently, regulatory mechanisms, often involving Hormones, must ensure a continuous supply of suitable fuel to all tissues under both normal feeding and fasting conditions. A breakdown in these mechanisms occurs during hormonal imbalances (e.g., under conditions of Insulin deficiency in diabetes), Metabolic Disorders during peak Lactation (e.g., Ketosis in cattle), or intensified metabolic processes during Pregnancy (e.g., pregnancy toxemia in sheep). Such conditions represent pathological deviations within the starvation syndrome, which is observed in many diseases accompanied by a loss of appetite.