Overview
The body mass index (BMI) is used an an estimate of body habitus that assesses the patient's weight in the context of their height, allowing for a more accurate measurement.
However, the BMI has several limitations - particular in its overestimation of obesity in people with a significant amount of muscle bulk.
BMI =
WeightHeight²
Classification
- Underweight - <18.5
- Normal - 18.5 - 24.9
- Overweight - 25 - 29.9
- Obese - 30 - 34.9
- Severely obese - 35 - 39.9
- Morbidly obese - 40+
Increased Body Mass Index
Body mass index > 25.
Associated with Obesity
- Metabolic syndrome - type 2 diabetes mellitus, hypertension, dyslipidaemia
- Ischaemic heart disease
- Stroke
- Respiratory - obstructive sleep apnoea, asthma
- Gastrointestinal - reflux, cholelithiasis, non-alcoholic steatohepatitis (NASH)
- Polycystic ovarian syndrome
- Osteoarthritis
- Varicose veins
- Gout
Reduced Body Mass Index
Body mass index <18.5
Associated with Being Underweight
- Hypoglycaemia
- Vitamin deficiency - scurvy, rickets
- Bone marrow suppression - anaemia, thrombocytopaenia, immunosuppression
- Cardiac - arrhythmia, MI
- Neurological - cognitive impairment, peripheral neuropathy, Wernicke-Korsakoff syndrome
- Muscle wasting
- Endocrine - osteoporosis, amenorrhoea
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