We wanted to gain a better understanding of the connection between calorie intake and obesity prevalence in the UK. An understanding of the connection between dietary behaviours and excess weight will help us prioritise between different food environment interventions and provide a guide to the overall scale of intervention needed to meet the healthy life mission’s goal. The aim of this work was to find out the answer to this question: how many fewer calories would people living with obesity need to eat on average to ensure halving obesity prevalence in England?

Obesity data is measured differently across the UK nations and the prevalence of obesity varies slightly. We intended to produce a similar study using data from Scotland in 2023 and we investigated the gaps in Welsh obesity data to understand what valuable analysis can be made there. Nonetheless, a broadly similar growth trend in obesity across the UK over the last 30 years suggests that a similar level of calorie reduction would be required to halve prevalence in each nation.

We undertook statistical modelling to help us answer the question. We compared and analysed data from the Health Survey from England from the years 1991-92 and 2019. This enabled us to calculate how much total weight people in the UK should lose to return to the early 1990s levels. We then used mathematical models to work out the quantity of calories that should be cut from diets across the UK to achieve this weight-loss goal. The dynamic mathematical model that we used is considered the gold standard in the field of obesity research and is made up of equations that simulate the biological processes (eg, loss in liquids and fat mass) that bring about weight loss when calorie intake is reduced.