Other conditions with a lifestyle component, such as lung cancer, are recognised as a disease, so why not obesity? Doing so would focus attention on improving prevention and treatment, rather than telling those with obesity to ‘try harder’, says Professor John Wilding.
The idea that obesity is a disease is not new:
‘Corpulency, when in an extraordinary degree, may be reckoned as a disease, as it in some measure obstructs the free exercise of the animal functions; and hath a tendency to shorten life, by paving the way to dangerous distempers’
Obesity develops over time when energy intake exceeds energy expenditure. Most excess energy in the body is stored as fat. When fat accumulates in the body it can limit mobility and put extra strain on joints, some of the excess fat may ‘spill over’ into other organs such as liver, muscle and pancreas, causing metabolic problems such as diabetes and fatty liver disease.
‘Corpulency, when in an extraordinary degree, may be reckoned as a disease, as it in some measure obstructs the free exercise of the animal functions; and hath a tendency to shorten life, by paving the way to dangerous distempers'
All of the known rare single gene variants leading to obesity do so by influencing the regulation of food intake. Most people with obesity are likely to have multiple variants with lesser individual effects, which makes them more likely to eat more. The amount of extra food is too small for most people to notice on a daily basis, but leads to obesity over many years.
It is also very hard to lose weight because the body responds to weight loss by changing the balance of gut hormones and neural signals to make us feel hungry; at the same time the body conserves energy by slowing metabolism. These signals may be stronger in people with obesity, making it even harder for them to lose weight and keep it off.
We now have extensive evidence from multiple epidemiological studies that obesity is associated with many complications which may be mechanical (the physical effects of the excess weight such as arthritis or sleep apnoea), metabolic (including type 2 diabetes, fatty liver, cardiovascular disease, and increased risk for some cancers) and mental (depression, anxiety, the effects of stigma). These complications are more likely to occur in the heaviest people and on average shorten life by about 12 years in those with severe obesity. So should obesity be classified as a disease? Let’s consider the arguments for and against.
Arguments for classifying obesity as a disease:
Arguments against classifying obesity as a disease:
Refutation of arguments against
[...] recognising obesity as a complex, relapsing disease with severe health consequences should help to focus attention on the need to provide comprehensive policies that aim to reduce the development of obesity in those at risk
In summary, recognising obesity as a complex, relapsing disease with severe health consequences should help to focus attention on the need to provide comprehensive policies that aim to reduce the development of obesity in those at risk, and provide evidence-based effective treatments for those who have already developed obesity, rather than exhorting them to ‘try harder’.
If that approach was used for people who had (for example) asthma (‘you need to work harder at your breathing’) or cancer cachexia (‘eat more’), or those with depressive illness to (‘be happier’ or ‘pull themselves together’) it would be quite rightly considered inappropriate advice, but that is exactly what those who advocate the approach that people with obesity should be simply eating less and moving more are saying. It is far more complicated than that.
Professor John Wilding leads clinical research into obesity at the University of Liverpool and specialist services for severe obesity at University Hospital Aintree and is president-elect of the World Obesity Federation.