Health Questions and Answers

Obesity

How is obesity currently defined?
Obesity is the level of overweightness associated with significant mortality and morbidity. Obesity is determined by body mass index (BMI). The BMI is calculated by dividing weight in kilograms by height in meters squared (weight in kg)/(height in meters)2. Individuals are currently considered overweight if the BMI is greater than 25. Levels of obesity are defined as follows:

  • BMI < 25: Normal
  • BMI 25-29.9: Overweight
  • BMI 30-34.9: Mild obesity
  • BMI 35-39.9: Moderate obesity
  • BMI > 40: Severe obesity

How significant is waist circumference in diagnosing obesity?
Waist circumference can also be used to diagnose obesity. Health risks of obesity are correlated with visceral (abdominal) adiposity. People with larger waist sizes have increased risks of obesity-related disorders such as hypertension, cardiovascular disease, and diabetes. Waist circumference is determined by placing a tape measure horizontally around the abdomen at the level of the iliac crest. Measurements should be taken at the end of a normal expiration. The tape measure should be snug but not compress the skin. Increased risk of obesity-related disease occurs in men with a waist circumference ≥ 40 inches (102 cm) and women with a waist conference ≥ 35 inches (88 cm).

List the health risks associated with obesity.

  1. Diabetes
  2. Hypertension
  3. Hyperlipidemia
  4. Coronary artery disease
  5. Cerebral vascular disease
  6. Degenerative arthritis
  7. Obstuctive sleep apnea
  8. Gallbladder disease
  9. Cancers of endometrium, breast, colon, and prostate
  10. Psychological complications (depression, poor self-esteem, discrimination)

How common is obesity?
Obesity is now thought to be one of the leading health disorders in the United States. Its prevalence has increased dramatically and it is now estimated that approximately one third of the U.S. population is obese (BMI > 30). The prevalence is higher in ethnic minorities and is rapidly increasing in children and adolescents.

What causes people to gain weight?
Weight gain occurs when a person is not in energy balance. Weight maintenance occurs when people consume as many calories as they expend per day. Obesity occurs in the setting of increased caloric intake or decreased energy expenditure relative to caloric intake.

List the three components of total daily energy expenditure (EE).

  • Basal metabolic rate (approximately 65% of total daily EE)
  • Energy of physical activity (30% of average person’s daily EE)
  • Thermic effect of food (energy cost of digesting food, which accounts for 5% of daily EE)

What factors control energy homeostasis?
Energy homeostasis is achieved by complex interactions between the brain and neural factors that control appetite and satiety, nutrient metabolism, and hormonal systems. Much research is currently being conducted in the neural mechanisms that regulate feeding and energy balance. Most evidence suggests that obese people do not have major alterations in their basal metabolic rates. In fact, since total energy expenditure is linearly related to BMI, obese people actually require more calories for weight maintenance than lean people. It is much more likely that obesity develops as a multifactorial process involving genetic predisposition as well as environmental and behavioral factors.

Who should be treated for obesity?
Obese people should be instructed about proper diet and exercise to prevent obesity-related complications. People with more severe obesity or those who already have obesity-related complications should be treated more aggressively.

Describe the general approach to treatment of obesity.
Treatment must be individualized, and the patient’s goals must be discussed. Frequently, patients want a rapid, substantial weight loss. Unfortunately, this goal is usually not healthy or attainable in the patient’s desired time frame. Since 1 lb of fat stores approximately 3500 kcal, in order to lose 1 lb of weight per week, the person must decrease caloric intake by roughly 500 kcal/day. This regimen is often extremely difficult to follow. Consequently, a more moderate approach is to restrict caloric intake (250-500 kcal reduction from basal intake) and increase energy expenditure (30 minutes of moderate physical activity most days of the week).

When should pharmacotherapy be considered for the treatment of obesity?
Typically, the first approach is diet and exercise with behavioral modifications followed by the addition of pharmacotherapy. Pharmacotherapy should be considered in patients with a BMI over 30, a BMI over 27 with comorbidities, or minimal response after 6 months of lifestyle modifications.

What medications are used for the treatment of obesity?

  • Phentermine, a norepinephrine agonist (15-30 mg/day)
  • Sibutramine, a combination norepinephrine/serotonin reuptake blocker (5, 10, and 15 mg; start with 10 mg and titrate)
  • Orlistat, a pancreatic lipase inhibitor (120 mg 3 times/day before meals)

How effective are medications in treating obesity?
In general, medications require chronic use for effectiveness and can be expected to produce a 5-10% weight loss in most people.

Summarize the role of surgery in the treatment of obesity.
Surgery is generally reserved for people with severe obesity (BMI > 40) who have failed other forms of therapy. The most frequently performed procedures are the vertical banded gastroplasty and gastric bypass.

References:

  • Stein CJ, Colditz GA: The epidemic of obesity. JCEM 89(6):2522-2525, 2004.
  • Larson PR, et al: Williams Textbook of Endocrinology, 10th ed. Philadelphia, W.B. Saunders, 2003.

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