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Justin M. Chu, M.D. and Jennifer Daily, M.D. Reviewed 06/2022

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Subject: Obesity

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  • A serious, progressive, and chronic disease characterized by excess adipose tissue, typically quantified in adults by body mass index (BMI) ([kg] / [m2]), ≥30 kg/m2

  • Overweight: BMI 25 to 29.9kg/m2

  • Obesity is categorized into three classes:

    • Class 1 obesity is BMI 30 to 34.9 kg/m2.

    • Class 2 obesity is BMI 35 to 39.9 kg/m2.

    • Class 3 obesity (also called severe obesity) is BMI ≥40 kg/m2.

  • Obesity is associated with negative health outcomes. Abdominal obesity increases the risk of morbidity and mortality.

Geriatric Considerations

Aging is associated with changes in body composition including sarcopenia, decreased bone mineral density, and accumulation of visceral fat.



Predominant age: Incidence rises in the early 20s and peaks at middle-aged adults 40-59 years old. 


  • 42% of U.S. adults classify as obese, and 68.5% classify as overweight or obese (1).

  • 17% of children and adolescents (2-19 years old) in the U.S. are obese and 32% classify as overweight or obese.

Pediatric Considerations
  • The USPSTF (United States Preventive Services Task Force) recommends screening for obesity in children and adolescents ≥6 years old and refer them to comprehensive, intensive behavioral interventions (grade B recommendation).

  • Pediatric classifications by age- and sex-specific WHO or CDC growth curves:

    • Overweight: BMI ≥85th-94th percentile

    • Obesity (Class I): BMI ≥95th percentile

    • Severe Obesity:

      • Class II: BMI ≥120th percentile of the 95th percentile

      • Class III: BMI ≥140th percentile of the 95th percentile

  • Obesity during adolescence is strongly associated with obesity in adulthood.

  • Obesity in children is associated with mental health and psychological issues, low self-esteem, and impaired quality of life (2).



  • Multifactorial process where genetic, environmental, behavioral, and psychosocial issues lead to an imbalance between energy intake and expenditure

  • After obesity has developed, an individual's neuronal signaling is altered to decrease satiety (3).

  • Adipocytes (fat cells) produce peptides called adiponectin and leptin. Adiponectin improves insulin sensitivity and the absence of leptin has been associated with severe obesity.


  • Genetic syndromes such as Prader-Willi and Bardet-Biedl are found in a minority of people with obesity.

  • Multiple genes are implicated in obesity and certain genotypes may account for differences in weight loss response following dietary changes (4).


  • Parental obesity

  • Sedentary lifestyle and lack of regular physical activity

  • Poor nutrition, especially consumption of calorie-dense food, and limited access to fresh produce/foods

  • Stress and mental illness


  • Encourage regular physical activity with a goal of at least 150 minutes of moderate activity per week (ex. 30 minutes of exercise, 5 days per week), and a well-balanced diet with appropriate portion sizes.

  • Avoid calorie-dense and nutrient-poor foods such as sugar-sweetened beverages and processed foods.

  • Early preventive counseling, especially in children and young adults


  • Type 2 Diabetes, HTN, hyperlipidemia

  • Coronary artery disease, congestive heart failure

  • Obstructive sleep apnea

  • Osteoarthritis

  • Nonalcoholic fatty liver disease

  • Mood disorders: anxiety, depression

  • Polycystic ovarian syndrome



  • Diet and exercise habits

  • Reported readiness to change lifestyle, and previous attempts at weight loss

  • Life stressors, social support, and resources


  • Physical Activity Vital Sign

    • Assess if patient achieves minimum goal of 150 minutes of moderate physical activity per week.

  • Waist circumference:

    • May be more important than BMI to assess obesity-associated health risks, especially in the elderly (sarcopenia)

    • Recommend measuring in patients with BMI 25-35 kg/m2.

    • Measure at the level of the umbilicus. Elevated:

      • Male: >40 inches (102 cm)

      • Female: >35 inches (88 cm)

  • Common abnormal findings: large neck habitus, acanthosis nigricans, striae


  • Cushing syndrome

  • Hypothyroidism

  • Undiagnosed concomitant primary psychiatric disorder


  • Screen for underlying physiologic causes as well as associated comorbid conditions.

  • Fasting blood glucose, hemoglobin A1C, lipid panel

  • Thyroid function tests

  • LFTs (non-alcoholic fatty liver disease)

Follow-Up Tests & Special Considerations

Fatigue may be related to underlying obstructive sleep apnea, and may warrant further investigation with sleep study. 



  • Assess:

    • Motivation to lose weight and patient-specific goals of therapy

    • Nutritional intake and physical activity habits

  • Goal is to achieve and sustain loss of at least ≥5% of body weight.

    • Weight loss is curvilinear with rapid weight loss at first, then slows until plateau.

  • USPSTF recommendation: "Encourage clinicians to promote behavioral interventions as the primary focus of the effective interventions for weight loss in adults."

  • Treat obesity-related comorbidities


  • Guidelines suggest at least 3-6 months of nonpharmacologic treatment with comprehensive lifestyle intervention alone prior to starting medications.

  • Consider pharmacotherapy in patients with a history of failure to achieve clinically meaningful weight loss (≥5% total body weight) and to sustain lost weight in patients who meet the following criteria:

    • BMI ≥30

    • BMI ≥27 + comorbidities (ex. CAD, diabetes, sleep apnea, HTN, hyperlipidemia)

  • Meta-analyses of randomized trials comparing pharmacologic therapy with placebo demonstrated that all active drug interventions are effective at reducing weight compared with placebo (5).

  • USPSTF found that pharmacotherapy combined with behavioral interventions was associated with greater weight loss and maintenance over 12-18 months than behavioral treatment alone (6)[A].

First Line

  • There are 9 FDA-approved medications for weight loss (5 for long-term use and 4 for short-term).

  • The most common side effects are GI related (nausea, vomiting, diarrhea, abdominal pain), unless otherwise specified.

  • Long-term treatment:

    • Liraglutide (Saxenda, Victoza):

      • GLP-1 agonist; preferred drug for patients with diabetes and cardiovascular disease. Can be prescribed for adolescents ≥12 years old

      • Dose: 0.6 mg subcutaneously daily for 1 week, and then increase at weekly intervals to target dose of 3mg daily

    • Semaglutide (Ozempic, Rybelsus, Wegovy):

      • GLP-1 agonist FDA approved for obesity in addition to diabetes

      • Dose: 0.25mg subcutaneously once weekly x4 weeks, and then increase dose at 4 week intervals to a target dose of 2.4mg once weekly

    • Phentermine /topiramate (Qysmia) likely most effective medication available:

      • Phentermine reduces appetite through increasing norepinephrine in the hypothalamus, and topiramate reduces appetite through its effect on GABA receptors. Schedule IV medication.

      • Dose: phentermine 3.75mg/topiramate 23 mg once daily for 14 days, then titrate up to 15 mg/92 mg once daily

      • Adverse effects: misuse potential, tachycardia, mood disorders, dry mouth, and topiramate is associated with fetal toxic effects (oral clefts).

    • Orlistat (Xenical):

      • Inhibitor of pancreatic lipase that reduces intestinal absorption of fat and increases excretion. FDA approved for ≥12 years old.

      • Dose: 120 mg 3 times daily with fat-containing meals

      • Adverse effects: GI (cramps, flatus, fecal incontinence, oily spotting). Should be taken with vitamin supplements because of slight decrease in fat-soluble vitamins (A, D, E, and K)

    • Naltrexone /bupropion (Contrave):

      • Naltrexone is an opioid antagonist that blocks effects of β-endorphins to reduce food intake. Bupropion reduces food intake by acting on adrenergic and dopaminergic receptors in the hypothalamus.

      • Dose: naltrexone 8 mg/bupropion 90 mg once daily for the first week, and up titrate to a goal of 16 mg/180 mg twice daily by week 4

      • Adverse effects: increased blood pressure, dry mouth, headache, insomnia

    • Plenity —Oral hydrogel of cellulose and citric acid creates feeling of fullness. Taken twice daily, 30 min before lunch and dinner with at least 16 oz of water. Relatively inexpensive

Second Line

  • Short-term use medications (<12 weeks) are older, sympathomimetic drugs that reduce food intake by causing early satiety. Adverse effects include increase in heart rate, blood pressure, insomnia, and dry mouth.

    • Phentermine: (Schedule IV medication)

      • Dose: 15 to 37.5mg daily or divided twice daily

    • Diethylpropion: (Schedule IV medication)

      • Dose: 25 mg 3 to 4 times daily before meals

    • Benzphetamine: (Schedule III medication)

      • Dose: Start at 25 mg once daily, and may titrate up to max dose of 50 mg 3 times daily.

    • Phendimetrazine: (Schedule III medication)

      • Dose: 17.5 to 35 mg 2 or 3 times daily taken 1 hour before meals


  • Physical activity

    • Results in additional 1-1.5 kg weight loss over 1 year in addition to dietary intervention alone (7)

    • Aerobic vs. resistance or high intensity vs. low intensity does not seem to affect overall weight loss.

  • Comprehensive Behavioral Therapy (CBT)

    • Components: 1) prescription of a moderately reduced-calorie diet, 2) program of increased physical activity, 3) behavioral strategies to facilitate adherence to diet and activity recommendations

    • Most effective in-person with high intensity (≥14 sessions in 6 months) by a trained interventionist


  • A referral for bariatric surgery is considered when other treatments have failed, BMI ≥35 + comorbidities, or BMI ≥40.

  • Associated with significant improvement in diabetes, sleep apnea, quality of life, depression, pain, and physical function (8)

  • Requires complex presurgical evaluation and follow-up in a skilled treatment center

  • Surgical procedures include biliopancreatic diversion, Roux-en-Y gastric bypass, sleeve gastrectomy, laparoscopic adjustable gastric banding, vagal blocking therapy, and gastric aspiration (AspireAssist).



  • Continue to discuss weight, lifestyle modifications, and address both current and new goals.

  • A new treatment plan should be implemented if no clinical meaningful weight loss after 3-4 months.


  • Long-term studies suggest net calorie reduction (~500 kcal/day) with a diet that a patient can adhere to is the best. Goal for women: 1200-1500 kcal/d, men: 1500-1800 kcal/d.

    • A reduction of 500 kcal/day can result in ~1 lb (0.45 kg) weight loss per week.

  • Very low calorie diet (200 to 800 kcal/day)

    • Produced significantly greater short-term weight loss but had similar long-term weight loss compared to low-calorie diets. Requires medical supervision

  • Mediterranean

    • Primarily plant-based foods, olive oil, nuts, legumes, whole grain, fruits, and vegetables. Fish and poultry multiple times per week

    • Meta-analysis showed decrease in bodyweight, BMI, Hemoglobin A1c, fasting glucose, and cardiovascular disease risk.

  • Balanced-nutrient, moderate calorie

    • Usually 1200-1800 kcal/d; ex. DASH diet

    • Based on MyPyramid food guide with emphasis on low saturated fat and ample fruits, vegetables, and fiber


Recommended website for FDA nutritional content in common foods: 


  • Patients who are obese compared to those with a normal weight are at an increased risk for many serious health conditions.

  • Patient motivation is associated with successful weight loss.


  • Cardiovascular disease

  • Osteoarthritis

  • Hypoventilation syndrome

  • Slipped Capital Femoral Epiphysis (SCFE) in children

  • Higher death rates from cancer: colon, breast, prostate, endometrial, gallbladder, liver, kidney


Ogden  CL, Carroll  MD, Flegal  KM. Prevalence of obesity in the United States. JAMA.  2014;312(2):189–190. [View Abstract on OvidMedline]
US Preventive Services Task Force, Grossman DC, Bibbins-Domingo K, et al. Screening for Obesity in Children and Adolescents: US Preventive Services Task Force Recommendation Statement. JAMA. 2017 Jun 20;317(23):2417-2426.
US Preventive Services Task Force, Curry SJ, Krist AH, et al. Behavioral Weight Loss Interventions to Prevent Obesity-Related Morbidity and Mortality in Adults: US Preventive Services Task Force Recommendation Statement. JAMA. 2018 Sep 18;320(11):1163-1171.
Bray GA, Heisel WE, Afshin A, et al. The Science of Obesity Management: An Endocrine Society Scientific Statement. Endocr Rev. 2018 Apr 1;39(2):79-132.
Khera R, Murad MH, Chandar AK, et al. Association of Pharmacological Treatments for Obesity With Weight Loss and Adverse Events: A Systematic Review and Meta-analysis. JAMA. 2016 Jun 14;315(22):2424-34. 
Yanovski SZ. Weight Management in Adults With Obesity: What Is a Primary Care Clinician to Do? JAMA. 2018 Sep 18;320(11):1111-1113.
Bray GA, Frühbeck G, Ryan DH, Wilding JP. Management of obesity. Lancet. 2016 May 7;387(10031):1947-56.
LeBlanc EL, Patnode CD, Webber EM, Redmond N, Rushkin M, O’Connor EA. Behavioral and Pharmacotherapy Weight Loss Interventions to Prevent Obesity-Related Morbidity and Mortality in Adults: An Updated Systematic Review for the U.S. Preventive Services Task Force [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2018 Sep. Report No.: 18-05239-EF-1. 



  • E66.9 Obesity, unspecified

  • E66.3 Overweight

  • R63.5 Abnormal weight gain

  • E66.8 Other obesity

  • E66.09 Other obesity due to excess calories

  • E66.01 Morbid (severe) obesity due to excess calories


  • 414916001 obesity (disorder)

  • 238131007 overweight (finding)

  • 161833006 abnormal weight gain (finding)

  • 450451007 Overweight in childhood (finding)

  • 238136002 Morbid obesity (disorder)


  • A majority of American adults are overweight or obese.

  • Modification in dietary and physical activity patterns remains the cornerstone of therapy. Consider bariatric surgery in patients with a BMI >40 who have failed more conservative treatment, particularly if there are associated risk factors.

  • Medication may be indicated when nonpharmacologic treatment for 3-6 months has been ineffective and the patient has a BMI >30 or a BMI >27 with associated risk factors.