Obesity, the accumulation of excess body fat, results when energy (caloric) intake exceeds energy expenditure (Fig. 26.10). Obesity is increasing in industrialized countries because of a reduction in daily energy expenditure and an increase in energy intake resulting from the increasing availability of palatable, inexpensive foods. The body mass index (BMI) is easy to determine and highly correlated to body fat. Nearly 69% of U.S. adults are overweight (BMI ≥25), and >33% of this group are obese (BMI ≥30). The anatomic distribution of body fat has a major influence on associated health risks. Excess fat located in the abdomen (upper body, apple shape), as reflected in waist size, is associated with greater risk for hypertension, insulin resistance, diabetes, dyslipidemia, and coronary heart disease as compared to fat located in the hips and thighs (lower body, pear shape). A person’s weight is determined by genetic and environmental factors. Appetite is influenced by afferent, or incoming, signals (that is, neural signals, circulating hormones such as leptin, and metabolites) that are integrated by the hypothalamus. These diverse signals prompt release of hypothalamic peptides (such as neuropeptide Y and α-melanocyte– stimulating hormone) and activate outgoing, efferent neural signals. Obesity is correlated with an increased risk of death and is also a risk factor for a number of chronic conditions. Weight reduction is achieved best with negative energy balance, that is, by decreasing caloric intake and increasing physical activity. Virtually all diets that limit particular groups of foods or macronutrients lead to short-term weight loss. Long-term maintenance of weight loss is difficult to achieve. Modest reduction in food intake occurs with pharmacologic treatment. Surgical procedures, such as gastric bypass, designed to limit food intake are an option for the severely obese patient who has not responded to other treatments.
Choose the ONE best answer. For Questions 26.1 and 26.2, use the following scenario.
A 40-year-old woman, 5 ft, 1 in (155 cm) tall and weighing 188 lb (85.5 kg), seeks your advice on how to lose weight. Her waist measured 41 in and her hips 39 in. The remainder of the physical examination and the blood laboratory data were all within the normal range. Her only child (who is age 14 years), her sister, and both of her parents are overweight. The patient recalls being overweight throughout her childhood and adolescence. Over the past 15 years, she had been on seven different diets for periods of 2 weeks to 3 months, losing from 5 to 25 lb each time. On discontinuation of the diets, she regained weight, returning to 185–190 lb.
6.1. Calculate and interpret the body mass index for the patient.
Body mass index (BMI) = weight in kg/(height in m)2 = 85.5/1.552 = 35.6. Because her BMI is >30, the patient is classified as obese.
6.2. Which one of the following statements best describes the patient?
A. She has approximately the same number of adipocytes as an individual of normal weight, but each adipocyte is larger.
B. She shows an apple pattern of fat distribution.
C. She would be expected to show higher-than-normal levels of adiponectin.
D. She would be expected to show lower-than-normal levels of circulating leptin.
E. She would be expected to show lower-than-normal levels of circulating triacylglycerols.