Obesity is having an excessive amount of body fat in relation to lean body mass that may impair health.
The primary cause is an energy imbalance between calories consumed and expended.
Treatment goals include to lose 5-10% of body weight or 0.5-1 kg (1-2 lb)/week for 6 months and regain of <3 kg in 2 years and sustained reduction of waist circumference of at least 4 cm.
Strategies are aiming for realistic goals and a multidisciplinary approach that is a combination of dietary change, physical activity and behavioral modification.

Obesity Diagnosis



  • Elicit the following in the history: Weight history, eating habits, physical activity, alcohol consumption, smoking, underlying diseases or conditions that hinder physical activities or weight loss, cultural and environmental factors affecting weight
  • Exclude secondary causes of obesity, such as medications (eg Insulin, Nateglinide, Repaglinide, Risperidone, Sertindole, Olanzapine, Clozapine, Mirtazapine, Valproate, Gabapentin), or history of genetic or endocrine disorders (eg hypothyroidism)
  • Detect potential comorbidities (eg type 2 diabetes mellitus (T2DM), hypertension, dyslipidemia, sleep apnea, hyperinsulinemia)
    • Its presence may affect the treatment decisions and outcomes
  • Assess psychologic mental status (eg patient’s self image, general mental health, stress factors, eating disorder, presence of depression and other mood disorders, substance abuse)
  • Detect pregnancy/lactation in women
    • Not usually recommended for weight loss program
  • Family history [eg obesity, presence of cardiovascular (CV) disease, hypertension, diabetes mellitus (DM), dyslipidemia, obesity-related cancer, thyroid disease]

Physical Examination

  • Blood pressure measurements
  • Physical exam for evidence of thyroid disease, Cushing’s syndrome, hypogonadism and dysmorphism


  • BMI
    • Measures relative weight for height
    • Indicates total body fat content
    • An accurate predictor of future health status, as raised body mass index (BMI) increases cardiovascular events or deaths, total mortality, diabetes mellitus, sleep disorder, osteoarthritis and certain cancers (eg endometrial, breast, colon)
    • Done annually for screening and as needed for management
    • Calculated by the formula: BMI = weight (kg)/[height (m)]2
      • Asian countries have lower BMI cut-off points for overweight and obesity than the WHO BMI values
    • Calculation is for all age groups; BMI percentile for age is used in children <18 years old to determine the healthy weight status 
  • Waist Circumference
    • Useful measurement of intra-abdominal fat content before and during weight loss treatment
    • Technique of choice for classifying central obesity and clinical risk
    • A large waist circumference is associated with an increased risk for diabetes mellitus, dyslipidemia, hypertension and cardiovascular disease in patients who may not be considered obese by conventional BMI criteria

Laboratory Tests

  • To assess comorbidities associated with obesity
    • Lipid profile [eg low-density lipoprotein cholesterol (LDL-C), HDL-C and triglyceride (TG)]
    • Fasting glucose level, A1C, thyroid function tests
    • Uric acid, liver function (hepatic enzymes), renal function
    • Urine free cortisol levels (perform in patients with signs of Cushing’s syndrome)
    • Lab tests to rule out polycystic ovarian syndrome
    • Electrocardiogram (ECG)
    • Chest X-ray


Risk Factor Assessment

Identify absolute risk status based on the presence of the following:

  • Disease Conditions
    • Coronary heart disease (CHD)
    • Atherosclerosis
    • Hypertension
    • Diabetes mellitus
    • Sleep apnea
    • Dyslipidemia
  • Other Obesity-Associated Diseases
    • Gynecological disorders (eg menorrhagia, amenorrhea)
    • Osteoarthritis (OA)
    • Asthma
    • Gallstones
    • Stress incontinence
    • Nonalcoholic fatty liver disease
    • Gastroesophageal reflux disease
  • Cardiovascular Risk Factors
    • Cigarette smoking
    • Hypertension
    • Hyperlipidemia
    • Impaired fasting glucose and impaired glucose tolerance
    • Family history of premature coronary heart disease (CHD) [eg myocardial infarction (MI) or sudden death in father/male 1st-degree relative at ≤55 years or mother/female 1st-degree relative at ≤65 years]
    • Age ≥45 years for men or age ≥55 years for women or postmenopausal
  • Others
    • Physical inactivity
    • Elevated serum triglycerides (>2.3 mmol/L) and decreased HDL-C


WHO Classification WHO BMI Cut-off Points (kg/m2) Risk of Comorbidities Asian BMI Cut-off Points (kg/m2)
Underweight <18.5 Low but increased risk of other clinical problems <18.5
Normal 18.5-24.9 Average 18.5-22.9
Overweight ≥25.0   ≥23.0
Pre-obese 25.0-29.9 Increased 23.0-27.4
Obese Class I 30.0-34.9 Moderate 27.5-34.9
Obese Class II 35.0-39.9 Severe 35.0-39.9
Obese Class III ≥40.0 Very severe ≥40.0
Race High-Risk Waist Circumference (cm)
Men Women
Caucasians ≥102 ≥88
Asians ≥90 ≥80
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