TABLE 1
Body mass index (BMI) and degrees of obesity
BMI | Category | Therapeutic options |
---|---|---|
<18.5 | Underweight | |
18.5–25.9 | Normal weight | Reinforce positive lifestyle |
25.0–29.9 | Overweight | Diet, exercise, behavior modification |
30.0–34.9 | Obese (Class I) | Diet, exercise, behavior modification; consider pharmacologic therapy* |
35.0–39.9 | Obese (Class II) | Diet, exercise, behavior modification; consider pharmacologic therapy |
≥40.0 | Obese (Class III or “Morbid Obesity”) | Consider surgical management |
*For patients with multiple cardiovascular risk factors (eg, diabetes, hyperlipidemia), BMI >27 may be an indication for pharmacologic intervention at; at BMI >37, patients may be considered candidates for surgical therapy. | ||
From the National Institutes of Health. Clinical guidelines on the identification, evaluation, and treatment of obesity in adults: the Evidence Report. Bethesda, Md: US Department of Health and Human Services, 1998. |
Evaluation of documented obesity
In history taking and physical examination, look for reversible causes of obesity (including medications and endocrine disorders), consider the degree of obesity, and determine whether comorbid conditions are present, to help estimate prognosis. Evaluate the patient’s dietary and exercise habits, as well as willingness to modify these habits if necessary.1,5 Finally, review the patient’s weight history and any attempts at weight loss.
Medications associated with weight gain include psychotropic drugs, anticonvulsant agents, steroid hormones, insulin, and many oral hypoglycemic agents.1
Endocrine disorders such as Cushing’s syndrome and hypothyroidism may also contribute to obesity, but only rarely. Physical findings that increase the likelihood of Cushing’s syndrome, and their respective positive likelihood ratios (LR+)— the higher the value, the greater the likelihood of disease—include: hypertension (2.3), moon facies (1.6), thin skinfold (115.6), ecchymoses (4.5), and acne (2.2).19 Findings, and their likelihood ratios, associated with hypothyroidism include coarse skin (5.6), cool/dry skin (4.7), bradycardia (4.1), enlarged thyroid (2.8), and hoarse voice (5.4).19 The very high LR for skinfold thickness was determined for women of childbearing age who had elevated risk of having Cushing’s syndrome because of a history of both menstrual irregularities and hirsutism. Skinfold thickness is determined by using calipers on an area of minimal subcutaneous fat (eg, back of the hand). For women of reproductive age, skinfold thickness is normally greater than 1.8 mm.19
Laboratory assessment of the obese patient will rarely find a cause of weight gain (eg, hypothyroidism), but the addition of selected diagnostic tests will aid in the determination of prognosis. An abnormal fasting glucose level or impaired glucose tolerance is a major risk factor for cardiovascular disease. Abnormal lipid profiles heighten that risk for obese patients. All patients with documented obesity should undergo assessment for abnormal lipids and impaired glucose tolerance5 (SOR: D).
Treatment
The most important step in treating obesity is to establish a calorie deficit. The deficit can be achieved by increasing energy expenditure or by reducing energy intake or absorption. On average, a caloric deficit of 500 kilocalories per day will result in a weight loss of 1 pound per week.5 Reasonable expectations of therapy include weight loss of 1–2 pounds a week and a loss of 10% of total body weight in 5 months.5
Interventions for weight loss fall into 4 categories: lifestyle modifications (diet, exercise, and behavioral modification), drug therapy, complementary or alternative measures, and surgery. Table 3 summarizes the levels of evidence to support each intervention.
TABLE 3
Efficacy of weight-loss interventions
Weight loss | ||||
---|---|---|---|---|
SOR* | Intervention | Short-term | Long-term | Comments |
Diet, exercise, and behavioral modification | ||||
A | Low/very-lowcalorie diet | 8% average weight loss from 3–12 months | Weight nears baseline in studies >24 months | Very-low-calorie diets may require laboratory assessment of metabolic function |
High rate of noncompliance | ||||
A | Low/very low fat with reduced calories | Similar to lowcalorie with moderate fat | Weight nears baseline in studies >24 months | No known side effects |
A | Exercise | Less weight loss than diet therapy | Likely no significant weight loss | Improved cardiovascular fitness |
May be effective in preventing weight gain | ||||
A | Low-calorie diet + exercise | Increased weight loss vs. diet or exercise alone | Weight nears baseline in long-term studies | Improved cardiovascular fitness |
Compliance a major problem | ||||
B | Behavior modification | Increases effectiveness of diet, exercise | No significant effect at 5 years | No reported harms |
Only studied when used with other methods | ||||
C | Lowcarbohydrate diet | Not significant if calories are not reduced | No long-term data available | No known side effects, but creates nutritional imbalance and ketosis |
Needs additional study | ||||
Medication | ||||
A | Sibutramine | ˜ 4 kg for trials less than 1 year | Modest weight loss when used for >1 year | Can elevate blood pressure |
Number needed to treat (NNT) for 5% weight loss at 1 year = 3 | ||||
NNT for 10% weight loss at 1 year = 5 | ||||
A | Orlistat | ˜ 2–3 kg for trials less than 1 year | ˜ 3 kg at 2 years | GI side effects common, possible vitamin deficiencies |
NNT for 5% weight loss at 1 year = 5 | ||||
NNT for 10% weight loss at 1 year = 7 | ||||
Surgery | ||||
B | Roux-en-Y Gastric bypass | ˜ 50 kg (110 lbs) at 1 year | ˜ 50 kg (110 lbs) at up to 4 years | Significant operative risk and post-operative GI side effects |
Nadir for weight loss occurs at 12–24 months | ||||
B | Gastric banding | ˜ 30 Kg (66 lbs) at one year | 10–15% of initial weight lost may be regained long-term | Significant operative risk and post-operative GI side effects |
Generally considered less effective that gastric bypass | ||||
Complementary/alternative medicine | ||||
B | Hypnosis | Minimal reduction | No statistically significant difference | Studied in combination with cognitive behavioral therapy |
Systematic reviews reveal significant heterogeneity of low-quality randomized controlled trials | ||||
B | Acupuncture | No significant difference | No significant difference | Systematic review reveals poor quality |
RCTs, which limits ability to determine effect | ||||
* Strength of recommendation | ||||
A = Systematic review of randomized controlled trials (RCT) (with homogeneity) or individual RCT with narrow confidence interval | ||||
B = Systematic review of cohort studies (with homogeneity), individual cohort studies or low-quality RCT, individual case-control study or SR of case-control studies (with homogeneity) | ||||
C = Case series and poor quality cohort and case control studies |