Obesity

Introduction

Obesity is a growing epidemic, particularly in developed countries, and is largely related to an unhealthy lifestyle.

Obesity is generally defined as excessive body fat mass.
The medical rationale for weight loss in people with obesity is that obesity is a disease associated with a significant increase in mortality and many health risks including type 2 diabetes mellitus, hypertension, dyslipidaemia, chronic kidney disease, osteoarthritis and coronary heart disease.

Body Mass Index (BMI)

Body size is typically defined using body mass index (BMI).

Normal weight 18.5-24.00 kg/m²
Overweight 25-29.99 kg/m²
Obese class I 30-34.99 kg/m²
Obese class II 35-39.99 kg/m²
Obese class III ≥40 kg/m²

Use caution when applying BMI to individuals with greater muscle mass, women or the elderly.

NOTE: Generally, Asians have a higher body fat percentage compared to Caucasians of the same age, sex and BMI. Even below the BMI cut-off of 25 kg/m², a substantial number of Asians develop diabetes and cardiovascular disease.

Goals of Treatment

The goal of therapy is to prevent, treat, or reverse the complications of obesity and improve quality of life.

Many patients, however, have a weight loss goal of 30% or more below their current weight, a goal that is often not achievable without bariatric surgery.

With lifestyle measures alone, a weight loss of 5 to 7% of body weight is more typical but often difficult to maintain.
In trials comparing pharmacologic therapy with placebo, weight loss of 5 to 10% using both drug and behavioural intervention is considered a very good response, and weight loss exceeding 10% is considered an excellent response.

Comprehensive Lifestyle Intervention

The initial management of individuals who would benefit from weight loss is a comprehensive lifestyle intervention.

Diet

Tailoring a diet that reduces energy intake below energy expenditure.

Increased physical activity

Physical activity should be performed for approximately 30 minutes or more, 5-7 days a week, to prevent weight gain and to improve cardiovascular health.

Behavioural modification

The goal of behavioural therapy is to help patients make long-term changes in their eating behaviour by modifying and monitoring their food intake, modifying their physical activity, and controlling cues and stimuli in the environment that trigger eating.
These concepts are usually included in programs conducted by psychologists or other trained personnel as well as many self-help groups.

Pharmacologic Therapy

Candidates for drug therapy include those individuals with a body mass index (BMI) ≥30 kg/m², or a BMI of 27 to 29.9 kg/m² with weight-related comorbidities, who have not met weight-loss goals (loss of at least 5% of total body weight at 3 to 6 months) with a comprehensive lifestyle intervention alone.

Glucagon-like peptide 1 (GLP-1) agonist (e.g. weekly semaglutide, daily liraglutide)

Is the preferred first-line pharmacotherapy for the treatment of obesity, particularly for patients with diabetes
Gastrointestinal side effects: nausea, vomiting.
Liraglutide: Discontinue use if the patient does not achieve at least a 4% weight loss after 16 weeks of therapy or if the patient cannot tolerate the target 3-mg daily dosage.

Orlistat

Inhibits pancreatic and gastric lipase, which reduces the absorption of fat from the gut.
The capsule should be taken immediately before, during or up to 1 hour after each main meal. If a meal is missed or contains no fat, the dose of orlistat should be omitted
Very common or common side effects relate to GI disturbances such as faecal urgency and incontinence, oily evacuation and spotting, flatus and abdominal pain.
Continue treatment beyond 12 weeks only if weight loss since start of treatment exceeds 5%.

Phentermine

Promote appetite suppression and decreased food intake secondary to its sympathomimetic activity.
All sympathomimetic drugs can increase heart rate and blood pressure and cause insomnia, dry mouth, constipation, and nervousness.
Only approved for the short-term (up to 12 weeks) treatment of obesity because of potential side effects, potential for abuse and regulator surveillance.

NOTE:

Liraglutide and phentermine are Group B poisons, whereas orlistat is Group C poison.
Although metformin does not produce enough weight loss (5%) to qualify as a "weight loss drug", it is a good choice for overweight individuals at high risk for diabetes.
Long-term safety of all agents is unknown.
Consider obesity as a chronic condition. Weight loss after discontinuation of agent is likely.

Bariatric Surgery

Surgical interventions (bariatric surgery), which may involve stapling, banding or bypassing of the stomach to reduce volume and so restrict intake are used.

Candidates for bariatric surgery include adolescents and adults with a BMI ≥40 kg/m², or a BMI of 35 to 39.9 kg/m² with at least one serious comorbidity, who have not met weight loss goals with diet, exercise, and drug therapy.

Dietary Supplements

Although over-the-counter dietary supplements are widely used by individuals attempting to lose weight, UpToDate advise against their use because evidence to support their efficacy and safety are limited. Examples of dietary supplements include ephedra, green tea, chromium, chitosan, and guar gum.

NOTE: Ephedra and ephedra alkaloids (Ma Huang), a group of ephedrine-like molecules found in plants, have been removed from the United States market because of safety concerns.

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