Being overweight or obese increases the risk of long-term and severe medical conditions. For example, around 85 per cent of people with high blood pressure have a BMI above 25kg/m². Other health conditions that are also more common in overweight and obese people include type 2 diabetes, kidney disease, heart disease, stroke and some types of cancer.

Weight also affects a person's life expectancy: someone who has a BMI of 30-35kg/m² loses an average of two to four years on their lifespan, while someone who has a BMI in excess of 40kg/m² lives an estimated average of eight to 10 years fewer than their counterparts who have a healthy body weight.