Chapter 041. Weight Loss (Part 2)

Energy balance and pathophysiology of weight loss. Food intake may be influenced by a wide variety of visual, olfactory, and gustatory stimuli as well as by genetic, psychological, and social factors. Absorption may be impaired because of pancreatic insufficiency, cholestasis, celiac sprue, intestinal tumors, radiation injury, inflammatory bowel disease, infection, or medication effect. These disease processes may be manifest as changes in stool frequency and consistency. Calories may also be lost due to vomiting or diarrhea, glucosuria in diabetes mellitus, or fistulous drainage. Resting energy expenditure decreases with age and can be affected by thyroid status. Beginning at about...
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Chapter 041. Weight Loss (Part 2) Chapter 041. Weight Loss (Part 2) Energy balance and pathophysiology of weight loss. Food intake may be influenced by a wide variety of visual, olfactory, andgustatory stimuli as well as by genetic, psychological, and social factors.Absorption may be impaired because of pancreatic insufficiency, cholestasis,celiac sprue, intestinal tumors, radiation injury, inflammatory bowel disease,infection, or medication effect. These disease processes may be manifest aschanges in stool frequency and consistency. Calories may also be lost due tovomiting or diarrhea, glucosuria in diabetes mellitus, or fistulous drainage.Resting energy expenditure decreases with age and can be affected by thyroidstatus. Beginning at about age 60, body weight declines by an average of 0.5% peryear. Body composition is also affected by aging; adipose tissue increases andlean muscle mass decreases with age. Significance of Weight Loss Unintentional weight loss, especially in the elderly, is relatively commonand is associated with increased morbidity and mortality rates, even aftercomorbid conditions have been taken into account. Prospective studies indicatethat significant involuntary weight loss is associated with a mortality rate of 25%over the next 18 months. Retrospective studies of significant weight loss in theelderly document mortality rates of 9–38% over a 2- to 3-year period. Cancer patients with weight loss have decreased performance status,impaired responses to chemotherapy, and reduced median survival (Chap. 77).Marked weight loss also predisposes to infection. Patients undergoing electivesurgery, who have lost >4.5 kg (>10 lb) in 6 months, have higher surgicalmortality rates. Vitamin and nutrient deficiencies may also accompany significantweight loss (Chap. 71). Causes of Weight Loss The list of possible causes of weight loss is extensive (Table 41-1). In theelderly, the most common causes of weight loss are depression, cancer, andbenign gastrointestinal disease. Lung and gastrointestinal cancer are the mostcommon malignancies in patients presenting with weight loss. In youngerindividuals, diabetes mellitus, hyperthyroidism, psychiatric disturbances includingeating disorders, and infection, especially with HIV, should be considered.Table 41-1 Causes of Weight LossCancer MedicationsEndocrine and metabolic Antibiotics Hyperthyroidism Nonsteroidal anti-inflammatory drugs Diabetes mellitus Serotonin reuptake inhibitors Pheochromocytoma Metformin Adrenal insufficiency LevodopaGastrointestinal disorders ACE inhibitors Malabsorption Other drugs Obstruction Disorders of the mouth and Pernicious anemia teethCardiac disorders Age-related factors Chronic ischemia Physiologic changes Chronic congestive heart failure Respiratory disorders Decreased taste and smell Emphysema Functional disabilities Chronic obstructive pulmonary Neurologicdisease Stroke Renal insufficiency Parkinsons disease Rheumatologic disease Neuromuscular disorders Infections Dementia HIV Social Tuberculosis Isolation Parasitic infection Economic hardship Subacute bacterial endocarditis Psychiatric and behavioral Depression Anxiety Bereavement Alcoholism Eating disorders Increased activity or exercise Idiopathic The cause of involuntary weight loss is rarely occult. Careful history andphysical examination, in association with directed diagnostic testing, will id ...