Presentation of obesity may range from asymptomatic to presentation complicated by multiple comorbidities, including cancer, coronary artery disease, diabetes, hypertension, gout, obstructive sleep apnea, and osteoarthritis. It is estimated that nearly 4 million people die each year as a consequence of weight-related comorbidities.
The definitive test for the diagnosis of obesity remains the body mass index (BMI; obesity is defined as a BMI ≥30 kg/m²).
Central or abdominal obesity has a stronger association with obesity-related comorbidity than peripheral (i.e., subcutaneous) obesity, so waist circumference may be a better indicator of the risk for obesity-related comorbidity than BMI.
The mainstay of nonsurgical treatment of obesity is diet and exercise, with psychological therapy as a recommended adjunct for all patients. The risk of complications is low, but the overall efficacy and durability of this combination is poor.
Drug therapy may be considered as an adjunct to diet and exercise (never as monotherapy) for patients with a BMI ≥30 kg/m². Pharmacotherapy has modest short-term efficacy but a high attrition rate and a lack of long-term efficacy.
Surgical treatment is an option for patients with BMI ≥40 kg/m², or ≥30 kg/m² with significant comorbidities. In general, weight-reductive surgery is performed through manipulation of the stomach or small bowel, or a hybrid of both. Potential complications are numerous, but have declined in recent decades. Studies now suggest that surgical treatment is more effective for severe obesity than nonsurgical treatment.
Obesity can be defined as a chronic adverse condition due to an excess amount of body fat. While there are many methods to determine the relative amount of body fat, the most widely used method to determine obesity is the body mass index (BMI), defined as weight divided by height squared ([weight in kg]/[height in m]²).
History and exam
Key diagnostic factors
Other diagnostic factors
- waist circumference
- comorbid conditions
- age ≥40 years
- peri- and postmenopause
- prior pregnancy
- sleep deprivation
- history of tobacco smoking
- less formal education
- poor in utero nutrition
- low socioeconomic status
- sedentary lifestyle
- television watching and video games >2 to 3 hours daily
- diet high in sugar, cholesterol, fat, and fast food
- heavy alcohol intake (>2 drinks per day)
- binge-eating disorder
- night eating syndrome
- leptin deficiency
- corticosteroid therapy
- antidepressant therapy
- antipsychotic therapy
- beta-blocker therapy
- adjuvant breast cancer therapy
- psychiatric diagnosis
1st investigations to order
- clinical exam
Investigations to consider
- serum aminotransferases
- thyroid function tests
- abdominal ultrasound scan
- polysomnography (sleep study)
BMI ≥30 kg/m²; or else BMI ≥27 kg/m² with an obesity-related comorbidity
BMI ≥40 kg/m²; or else BMI ≥35 kg/m² with significant comorbidities and dietary attempts at weight control have been ineffective
Constantine T. Frantzides, MD, PhD, FACS
Director, Chicago Institute of Minimally Invasive Surgery (CIMIS)
Director, Laparoscopic and Bariatric Fellowship Program
Clinical Professor of Surgery, University of Illinois
CTF declares that he has no competing interests.
Mark A. Carlson, MD, FACS
Professor, Department of Surgery
Professor, Department of Genetics, Cell Biology and Anatomy (courtesy)
Director, Center for Advanced Surgical Technology (CAST)
University of Nebraska Medical Center
Staff Physician, Surgery Department
Omaha VA Medical Center
MAC declares that he has no competing interests.
Kelsey R. Tieken, MD
General Surgery Resident
University of Nebraska Medical Center
KRT declares that she has no competing interests.
Dr Constantine T. Frantzides, Dr Mark A. Carlson, and Dr Kelsey R. Tieken would like to gratefully acknowledge Dr Minh B. Luu and Dr Scott N. Welle, previous contributors to this topic.
MBL and SNW declare that they have no competing interests.
Carel Le Roux, MRCP, PhD, FRCPath
Consultant in Metabolic Medicine
Imperial College London
Charing Cross Hospital
CLR declares that he has no competing interests.
Arya M. Sharma, MD, PhD, FRCPC
Professor of Medicine
Chair for Obesity Research & Management
University of Alberta
Royal Alexandra Hospital
AMS declares that he has no competing interests.
Edward H. Livingston, MD, FACS
Chair in Surgery
Division of Gastrointestinal and Endocrine Surgery
University of Texas
Southwestern Medical Center
EHL declares that he has no competing interests.
- Hypothyroidism, primary
- Hypothyroidism, central
- Cushing syndrome
- ASMBS position statement on the rationale for performance of upper gastrointestinal endoscopy before and after metabolic and bariatric surgery
- AGA clinical practice guidelines on intragastric balloons in the management of obesity
Obesity - diet and exercise
Obesity - drugs and surgeryMore Patient leaflets
Body Mass Index (Quetelet's index)More Calculators
- Log in or subscribe to access all of BMJ Best Practice
Use of this content is subject to our disclaimer