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Overweight and obesity

Last updated: September 18, 2025

Summarytoggle arrow icon

Overweight and obesity are characterized by an accumulation of excess body fat associated with the risk of developing weight-related complications. Multiple underlying factors (e.g., genetics, hormonal changes, lifestyle behaviors, medical conditions, medication use) ultimately result in prolonged excess energy intake relative to energy expenditure. Body mass index (BMI) and waist circumference are used to diagnose and classify overweight and obesity, and to estimate the risk of weight-related complications. Clinical evaluation and diagnostic studies are used to assess for contributing causes of overweight and obesity and weight-related complications (e.g., hypertension, cardiovascular disease, dyslipidemia, diabetes). Management focuses on weight loss and preventing or improving weight-related complications, and should be individualized based on shared decision-making. Management options include lifestyle changes (dietary changes, increased physical activity, and/or behavioral interventions), pharmacotherapy, and bariatric surgery. Interventions are often performed concurrently.

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Epidemiologytoggle arrow icon

Epidemiological data refers to the US, unless otherwise specified.

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Etiologytoggle arrow icon

Overweight and obesity are caused by prolonged excess energy intake relative to energy expenditure. Contributing factors include: [3][4][5]

Chronic sleep deprivation can lead to obesity through multiple mechanisms (e.g., increased caloric intake, sedentary lifestyle, and hormonal imbalance). [4][5]

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Classificationtoggle arrow icon

General principles

Body mass index [6][9][10][11]

BMI classification for overweight and obesity [6][9][10][11]

Adults (absolute BMI) Children aged ≥ 2 years (BMI percentile for age and sex) [4][15]
Overweight
  • Most populations: 25–29.9 kg/m2
  • Asian descent: 23–24.9 kg/m2 [16][17]
Class 1 obesity
  • Most populations: 30–34.9 kg/m2
  • Asian descent: 25–29.9 kg/m2 [16][17]
Class 2 obesity
  • Most populations: 35–39.9 kg/m2
  • Asian descent: 30–34.9 kg/m2
Class 3 obesity
  • Most populations: ≥ 40 kg/m2
  • Asian descent: ≥ 35 kg/m2

To determine class 2 or class 3 obesity in children, use the adult BMI cutoff if it is lower than the pediatric BMI percentile for age and sex cutoff. [4]

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Clinical featurestoggle arrow icon

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Diagnosistoggle arrow icon

Overweight and obesity in children and overweight and obesity in pregnancy (including preconception care) are addressed separately.

Approach [3][6][8][18]

Screening for metabolic syndrome is performed as part of the clinical evaluation and routine studies in patients with obesity. [6]

Clinical evaluation for overweight and obesity [3][6][19]

Address any acute problems and obtain the patient's permission before discussing weight. [13][20][21]

History

Review of symptoms

Physical examination

Use an appropriately sized blood pressure cuff; extended cuffs may be necessary. [16]

Studies for weight-related complications [3][6][19]

Routine studies

Further studies

Obtain further studies based on clinical suspicion for weight-related complications. Examples include:

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Managementtoggle arrow icon

Overweight and obesity in children and overweight and obesity in pregnancy (including preconception care) are addressed separately.

Approach [3][6][8][14][16]

A trial of lifestyle modifications alone is not required before initiating pharmacotherapy in patients with indications for weight-loss medications. [16]

Even small weight losses (e.g., 3–5% of body weight) can decrease the risk of weight-related complications. [6][16][25]

Medications associated with weight changes

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Lifestyle interventionstoggle arrow icon

General principles [3][6][7]

Dietary changes [6][7][18]

  • Provide general counseling on nutrition.
  • Various dietary approaches that result in a caloric deficit may be effective for weight loss.
  • Refer to a dietitian for specific caloric and energy deficit recommendations. [6][7][8]

Physical activity [6][7][26][27]

  • Provide counseling on regular exercise.
    • No specific form of physical activity is recommended over another for weight loss.
    • Encourage gradually increasing quantity and/or intensity of activity as tolerated to meet recommendations and weight-loss goals. [26][27]
  • Encourage an increase in nonsedentary activities. [8]
  • Additional guidance: exercise coach or physical therapy referral

Behavioral interventions [6][7][18][25]

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Pharmacotherapytoggle arrow icon

General principles [5][8][16][25][28]

  • Offer pharmacotherapy in conjunction with lifestyle modifications to patients with indications for weight-loss medications:
    • BMI ≥ 30 kg/m2
    • BMI ≥ 27 kg/m2 and at least one weight-related health problem
  • Choose a medication based on indications, contraindications, and patient preference.
  • Titrate medications gradually to improve tolerance.
  • Weight-loss goals
    • Initial: ≥ 5% from baseline at 3 months on maximum tolerated dose [8][25]
    • Long-term: ≥ 5–15% from baseline [6][16]
  • Follow-up
    • Frequency: monthly for 3–6 months, and then less frequently [7][8][16]
    • Monitor for adverse effects, including cholelithiasis and mood disorders. [6]
    • If weight-loss goals are not met, consider changing to an alternative medication and/or referral to an obesity specialist.
    • Long-term use of medications is typically required for sustained weight loss.

Medications

Pharmacotherapy for weight loss [5][8][16][25][28]
Drug class Examples Indications Considerations
Nutrient-stimulated hormone-based medications
  • Advise patients on management strategies for common GI side effects.
  • Restart dose titration if 2–3 consecutive doses are missed. [16][30]
  • Monitor for adverse effects (e.g., pancreatitis, gallbadder disease, malnutrition, and sarcopenia). [30]
Centrally acting medications
Lipase inhibitors
  • Not routinely recommended; may be selected based on patient preference [25]
  • Advise patients to:

Due to the teratogenicity risk, advise patients who can become pregnant to use contraception while taking pharmacotherapy for obesity. [7][25][31]

Tirzepatide has the highest efficacy in terms of total weight loss compared to other weight-loss drugs. [16]

Orlistat reversibly inhibits gastric and pancreatic lipase, resulting in a decrease in fat breakdown and absorption, and can cause gastrointestinal side effects.

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Metabolic and bariatric surgerytoggle arrow icon

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Complicationstoggle arrow icon

Cardiometabolic weight-related complications [6][8][33][34]

The co-occurence of central obesity, T2DM or prediabetes, hypertension, and dyslipidemia is known as metabolic syndrome. [33]

Additional weight-related complications [6][8]

We list the most important complications. The selection is not exhaustive.

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Preventiontoggle arrow icon

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Special patient groupstoggle arrow icon

Overweight and obesity in children [4]

Diagnostics

Suspect genetic causes of obesity in children with class 2 obesity or higher at ≤ 5 years of age with hyperphagia and/or other syndromic features. [4][50]

Management [4][52][53]

Overweight and obesity in pregnancy [31]

Preconception

Pregnancy

Obesity-related complications during pregnancy comprise maternal complications (e.g., pregnancy loss, gestational diabetes, preeclampsia, cesarean delivery, postpartum hemorrhage) and fetal complications (e.g., neural tube defects, hydrocephalus, anatomic abnormalities). [31]

Delivery and postpartum [31]

Pharmacotherapy for obesity is contraindicated during pregnancy and breastfeeding due to the risk of adverse effects in the fetus or infant. [6][25]

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