20th February 2024

Epidemiology

The incidence of obesity is rising worldwide, with up to 1 in 4 adults in the UK classified as obese. This appears to be worse in the lower socioeconomic populations and those of African, Caribbean and Pakistani descent. Modifiable obesity-related factors include food consumption, physical activity and psychological factors. Other non-modifiable factors include genetics, associated medical conditions and medication use. 

The body mass index (BMI) identifies and quantifies obesity. The cut-off utilised by NICE is as follows:

• Healthy – 18.5-24.9kg/m²
• Overweight – 25-29.9 kg/m²
• Obesity I – 30 – 34.9 kg/m²
• Obesity II – 35-39.9 kg/m²
• Obesity III – ≥ 40 kg/m²

In addition, waist circumference is also utilised in patients with BMI<35kg/m² to identify obesity-related problems. A waist circumference of ≥ 94cm in males and ≥ 80cm in females indicates an increased risk for obesity-related problems. 

Obesity is caused by a mismatch between energy intake and expenditure, with its direct pathophysiology not wholly known. Hormones like leptin and ghrelin have been shown to affect the central nervous system regarding appetite.