Question to the Department of Health and Social Care:

To ask His Majesty's Government what data describes the differing causes of obesity (1) with and without malnutrition, and (2) in people of high and low economic placement.

Obesity is a complex problem caused by numerous factors, to which there is no single solution. The National Institute for Health and Care Excellence (NICE) recommends that body mass index (BMI) is used to assess obesity in adults and children. Additionally, it recommends the use of other validated obesity measures, such as waist circumference, to be undertaken alongside BMI for adults when assessing overweightness and obesity in individuals to give a more detailed assessment of an individual’s health risk.

Malnutrition as a broad term refers to deficiency, excess or imbalances of a person’s intake of calories, protein and other nutrients which causes measurable adverse effects on body composition, function or clinical outcome. The full definition of malnutrition therefore includes overnutrition which can lead to obesity, however, in the United Kingdom, the term is more commonly used to refer to a clinical condition involving undernutrition.

NICE advises that nutrition support should be considered in people who are malnourished, as defined by any of the following: a BMI of less than 18.5 kilograms/m²; unintentional weight loss greater than 10% within the last three to six months; or a BMI of less than 20 kilograms/m² and unintentional weight loss greater than 5% within the last three to six months.

Someone can therefore be a healthy weight or have a BMI in the overweight or obese categories but be identified through the NICE definition as potentially requiring nutrition support. The term ‘malnutrition’ is sometimes incorrectly used to refer to a poor diet; although this may put someone at increased risk of malnutrition, this would not necessarily meet the criteria for malnutrition.

Data is not collected on causes of obesity. Data from the Health Survey for England, 2021 and National Child Measurement Programme show obesity prevalence was lowest for those living in the least deprived areas and highest in the most deprived areas.