Obesity is a complex, chronic disease influenced by a range of factors, including our genes, the environment we live in and underlying health conditions.1-3
Understanding these factors is crucial, because obesity is associated with other diseases, including type 2 diabetes, heart disease and certain types of cancer.2 People living with obesity also often face stigma and discrimination in the workplace, educational environments, healthcare settings, and society in general, which can impact their physical and mental health.4
Obesity is influenced by many factors both inside and outside the body.2,3 A person could be born with a tendency to put on weight, just as someone is born with a particular eye colour.7
There is also the physiological aspect. When a person eats, hormone signals from the stomach and gut are translated into feelings of reduced hunger and increased satiety, impacting food intake.8 Hormone levels during weight loss can change to make people feel hungrier and slow down energy expenditure – this is the body’s attempt to regain the lost weight.9
All of this means losing weight, and keeping it off, can prove challenging. But with the right care and support, people living with obesity can achieve sustained, substantial weight loss.10
To understand obesity, we must understand what is going on in our brains. It seems our bodies are hard-wired to hang on to those extra calories, probably because for thousands of years, it was a basic survival mechanism.9
Therefore, people living with obesity struggle to lose weight. Their body's programming works to get them back to their original starting weight. In the brain, it's as if there is a switch that tweaks a person’s energy expenditure until they have regained the lost weight.9
We are trying to pinpoint where exactly in the brain such a 'switch' could be located and exploring whether it is something we could address.
Today, we know that obesity is a serious chronic disease and not a matter of willpower.1-3
We are committed to driving change in how the world sees, prevents and treats obesity. As leaders within the science of obesity, we are working to make obesity a healthcare priority, defeat stigma and support better access to evidence-based care.
Bray GB et al. Obesity: a chronic relapsing progressive disease process. A position statement of the World Obesity Federation. Obes Rev. 2017;18(7):715-723; doi: 10.11 11/obr.12551
NHS UK. Obesity; 15 February 2023. Available from: https://www.nhs.uk/conditions/obesity [Accessed April 2025]
WHO. Obesity and overweight; 1 March 2024. Available from: https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight [Accessed April 2025]
Rubino F et al. Joint international consensus statement for ending the stigma of obesity. Nat Med. 2020;26(4):485-497; doi: 10.1038/s41591-020-0803-x
A Novo Nordisk commissioned report. Frontier Economics. Estimating the full costs of obesity; 26 January 2022. Available from: https://www.frontier-economics.com/media/hgwd4e4a/the-full-cost-of-obesity-in-the-uk.pdf [Accessed April 2025]
Cancer Research UK. New analysis estimates over 21 million UK adults will be obese by 2040; 19 May 2022. Available from: https://news.cancerresearchuk.org/2022/05/19/new-analysis-estimates-over-21-million-uk-adults-will-be-obese-by-2040/ [Accessed April 2025]
Gadde KM et al. Obesity: pathophysiology and management. J Am Coll Cardiol. 2018;71(1):69-84; doi: 10.1016/j.jacc.2017.11.011
Yeung AY and Tadi P. NCBI Bookshelf. Physiology, Obesity Neurohormonal Appetite and Satiety Control; 3 January 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK555906/ [Accessed April 2025]
Sumithran P and Proietto J. The defence of body weiqht: a physioloqical basis for weiqht reqain after weiqht loss. Clin Sci. 2013;124(4):231- 241; doi: 10.1042/(520120223
Spreckley M et al. Perspectives into the experience of successful, substantial long-term weight-loss maintenance: a systematic review. Int J Qual Stud Health Well-being. 2020;16(1):1862481; doi: 10.1080/17482631.2020.186248