[GitHub repo][1] **Objectives**: Excess weight prevalence in England has increased rapidly in the last 30 years (Health Survey for England 2022). Nesta has the goal of contributing to halving the obesity prevalence in the UK by 2030 from its 2020 levels and it intends to do so by designing, testing and scaling interventions in the food environment that impact at population level. Obesity prevalence in the early 1990s was half that measured in 2020, so achieving Nesta’s goal would be consistent with taking obesity levels back three decades. This study provides an estimate of the average reduction in daily calories required for the English population to lose enough weight to halve the obesity rate over the next 10 years. Future directions for this work include an assessment of the extent to which current government interventions have been able to produce a reduction consistent with the calculated target and what other food environment interventions might be considered to meet the target. **Design**: In order to provide a population level benchmark for calorie reduction, Nesta developed a novel methodology based on the comparison of historical Body Mass Index (BMI) distributions. The methodology consists of the following steps. Firstly, the BMI distributions from 1991-92 and 2019 are equivalised using representative samples from the Health Survey of England. The equivalising exercise is to determine the average reduction in body weight that people in each BMI class (underweight, healthy weight, overweight, obese and morbidly obese) would need to experience for the BMI distribution to change its shape and location to match that of 1991-92 (when obesity prevalence was roughly half what we have today). Secondly, the reduction in daily calorie intake is calculated that each respondent of the 2019 Health Survey for England would need in order to lose enough weight to meet the target goal defined by comparing the BMI distributions in the first step. The reduction in daily calories has been calculated using the model developed by Hall et al. (2011), which is considered the gold standard in the field and it was also the basis of the Department for Health and Social Care’s Calorie Model (Department of Health and Social Care 2018). **Setting**: The Health Survey for England 1991 and 2019 (cross-sectional data on height, weight and BMI). **Results**: The reduction in calories required for individuals with excess weight (BMI higher than 25 kg/m2) in England is around 8.5% of current intake for both females (190 kcal/day) and for males (241 kcal/day). When results are broken down by BMI group within the excess weight group, there is variation in the calorie reduction required. The required reduction is larger for higher BMIs with figures for overweight males being at 6.9% (187 kcal/day), obese males at 10.3% (307 kcal/day) and morbidly obese males at 14.8% (531 kcal/day). For females, the figure for overweight categories is a 6.5% reduction (136 kcal/day), for obese ones is 9.6% (222 kcal/day) and for morbidly obese groups is 13.7% (395 kcal/day). Under the assumption of no change in daily intake for underweight and healthy weight BMI groups, at population level and across all BMI groups these figures translate to an average of 165 kcal/day for males and 115 kcal/day for females. he reduction in calories are calculated within a timeframe of three years and for groups of individuals in separate BMI categories and for the group of people with excess weight as a whole (overweight, obese and morbidly obese). Population level figures are also provided under the assumption that BMI groups in the underweight and healthy weight categories do not change calorie intake. **Conclusions**: This study contributes to the debate around obesity reduction in England with the aim of providing a robust figure of a population level benchmark for aggregate calorie reduction. Whilst acknowledging the difficulty of synthesising complex biological processes in tractable equations and of collecting anthropometric measurements at large scale, this study uses gold standard methods and the most up to date and comprehensive dataset for England to produce a robust figure for calorie reduction at population level, and across BMI groups. [1]: https://github.com/nestauk/ahl_weight_loss_modelling