Porth's Essentials of Pathophysiology, 4e

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Integrative Body Functions

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malabsorption disorders. In contrast, clinical eating disorders are caused by psychiatric illness. Protein-Energy Malnutrition Protein-energy malnutrition represents a depletion of the body’s lean tissues caused by starvation or a com- bination of starvation and catabolic stress. The lean tis- sues are the fat-free, metabolically active tissues of the body, namely the skeletal muscles, viscera, and cells of the blood and immune system. Because lean tissues are the largest body compartment, their rate of loss is the main determinant of total body weight in most cases of protein energy malnutrion. Much of the literature on malnutrition and starva- tion has dealt with infants and children in underdevel- oped countries in which food deprivation results in an inadequate intake of protein and calories to meet the body’s energy needs. Protein-energy malnutrition in this population commonly is divided into two distinct conditions: marasmus (protein and calorie deficiency) and kwashiorkor (protein deficiency). The pathologic changes for both types of malnutrition include humoral and cellular immunodeficiencies resulting from pro- tein deficiency and lack of immune mediators. There is impaired synthesis of pigments of the hair and skin (e.g., hair color may change and the skin may become hyperpigmented) due to a lack of substrate (tyrosine) and coenzymes. There are two functional compartments involved in the distribution of proteins within the body: the somatic compartment , represented by the skeletal muscles, and the visceral compartment , represented by protein stores in body organs, principally the liver. 42 These two com- partments are regulated differently, with the somatic compartment being affected more severely in marasmus and the visceral compartment affected more severely in kwashiorkor. Marasmus represents a progressive loss of muscle mass and fat stores due to inadequate food intake that is equally deficient in calories and protein. 42,43 It results in a reduction in body weight adjusted for age and size. The child with marasmus has a wasted appearance, with loss of muscle mass, stunted growth, and loss of subcutaneous fat; a protuberant abdomen (from muscular hypotonia); wrinkled skin; sparse, dry, and dull hair; and depressed heart rate, blood pressure, and body temperature. Diarrhea is common. Since immune function is impaired, concurrent infec- tions occur and place additional stress on an already weakened body. An important characteristic of maras- mus is growth failure; if sufficient food is not pro- vided, these children will not reach their full potential stature. 43 Kwashiorkor results from a deficiency in protein in diets that are relatively high in carbohydrates. 42,43 The term kwashiorkor comes from an African word meaning “the disease suffered by the displaced child,” because the condition develops soon after a child is displaced from the breast after the arrival of a new infant and placed on

■■ The risks associated with obesity include hyperlipidemia, insulin resistance, and SUMMARY CONCEPTS (continued)

hypertension, which together predispose to the development of type 2 diabetes mellitus and atherosclerotic cardiovascular disease (e.g., coronary artery disease, stroke). Obesity is also associated with gallbladder disease, infertility, osteoarthritis, sleep apnea, complications of pregnancy, menstrual irregularities, nonalcoholic fatty liver disease, thromboembolic disorders, and poor wound healing. ■■ Childhood obesity is becoming an increasingly prevalent nutritional disorder that predisposes children and adolescents to hypertension, dyslipidemia, type 2 diabetes mellitus, and psychosocial stigma.

Undernutrition and Eating Disorders

Undernutrition continues to be a major health problem throughout the world. 40 Protein-energy malnutrition is most obvious in developing countries of the world, where it is indirectly responsible for half of all deaths of young children. 41 Even in developed nations, malnutri- tion remains a problem. Malnutrition and Starvation Malnutrition and starvation are conditions in which a person does not receive or is unable to use an adequate amount of nutrients for body function. An adequate diet should provide sufficient energy in the form of carbo- hydrates, fats, and proteins; essential amino acids and fatty acids for use as building blocks for synthesis of structural and functional proteins and lipids; and the necessary vitamins and minerals to function as coen- zymes or hormones in vital metabolic processes or, as in the case of calcium and phosphate, as important struc- tural components of bone. 42 Among the many causes of malnutrition are poverty and lack of knowledge about nutritional needs, acute and chronic illness, and self-imposed dietary restric- tions. Homeless people, the elderly, and the children of the poor often demonstrate the effects of protein and energy malnutrition, as well as vitamin and min- eral deficiencies. Even the affluent may fail to recognize that infants, adolescents, and pregnant women have increased nutritional needs. Some types of malnutri- tion are caused by acute and chronic illnesses, such as