Imagine you’re obese. Would you describe yourself as “diseased”? The American Medical Association would. In 2013, it decided obesity was a disease. This was mainly, it must be said, for

pragmatic reasons, to “help change the way the medical community tackles this complex issue”. Or, as somebody far more cynical than I might say, in order to give doctors something else they

could bill health insurers for. Not everyone was convinced. Obesity, critics argued, lacks a tightly defined set of symptoms (you don’t get a fever or break out in spots) and specific

functional impairments. Obesity may be one of the causes of diseases such as diabetes, but surely calling it a disease in itself was drawing a long bow, they claimed. This is more than a

agent that carries and transmits the disease), they’re communicable and have a well-defined set of signs and symptoms. A little further out from the centre, we might find depression, which

has specific diagnostic criteria, appears to be treatable by common drugs such as anti-inflammatories, but is not really communicable. Far from the centre, we might see, say, cerebral palsy.

Is it a disease at all, or a condition? And then there are “diseases” such as irritable bowel syndrome and repetitive strain injury, which whizz in and out of our disease solar system like

haywire comets. Diseases share a number of characteristics, but not all diseases have all those characteristics. They follow a pattern that the philosopher Wittgenstein called “family

resemblances”. Obesity certainly has some disease characteristics. It has a clear diagnostic criterion – a BMI of 30 or more. It has a known set of common symptoms (high blood fats, for

instance, and poor blood sugar regulation). Obesity may even be communicable through social networks. One study found that a person’s chances of becoming obese increased by 57% if they had a

friend who became obese. And obesity has a recommended treatment: diet and exercise — but we’ll come to that in a minute. OBESITY AS DISEASE Most people agree that if obesity is a disease,

it’s out there on the fringes of the solar system. While declaring a condition to be a disease is rather like deciding whether Pluto is a planet (call it what you like, it’s still out

there), it has very important practical implications. If I’m obese and obesity is a disease, I can reasonably expect the government and health funds to cough up money for my treatment,

researchers to be funded to explore causes and cures, and pharmaceutical companies to be reimbursed for developing their magic pills. I could sue those responsible for giving me the disease

or for failing to take reasonable steps to prevent it (just who did put the Coke machine at the base of the lift?). A lot of people — doctors, lawyers, researchers, pharma — have a lot of

skin in the game and their common interests in manufacturing illness may be just a little too closely aligned. And if I’m obese, I have skin in the game, too. Now that I’m a person with a

disease, I feel the burden of blame and uncertainty lift from my shoulders. Diseases just happen to people. Nobody blames a person for having Ebola. It takes the pressure off me to treat

myself; I become a medical problem. I feel the reassuring passivity of the patient in the hands of doctors and nurses – my treatment has been socialised. I am no longer solely responsible

for sticking to monastic diets, or the endless hours of preening and pec-flexing at the gym. BITTER PILL But will it do me any good? Six years ago, the American College of Sports Medicine

launched its “Exercise is Medicine” campaign with the words: > According to a recently released study, it’s estimated that half > of all adults in the US will be obese by the year 

2030. But a new opinion piece in The Lancet has suggested that diet and exercise are about as useful as an ashtray on a motorbike. Indeed, diet and exercise interventions have a very poor

record of long-term success. One review found that, after five years, the average weight loss from diet or exercise interventions – or a combination of both – was just three kilograms. One

reason for this is that obese adults have more fat cells, and therefore greater fat storage capacity. Long-term obesity also leads to an enhanced neurochemical response to food rewards (you

know, that thrilling surge of dopamine when the Ferrero-Rochers go from the plate to the palate). What’s more, when you’ve been obese for a long time, your body resets its idea of what

weight you should be — the body weight setpoint — and it becomes very hard to shift. In fact, obese people are swimming against a much stronger biological tide than the lean and are being

swept out by the rip, drowning not waving. The authors of The Lancet article recommend we turn to drugs and bariatric surgery (stomach-stapling) as they are “the only available treatment to

show long-term effectiveness”. Essentially, as far as treating obesity is concerned, diet and exercise are like medicines that we know will work, but which taste so bad that nobody will take

them. But the main problem with the scalpel-and-drugs approach is that exercise and diet have benefits regardless of weight loss. A number of studies show it’s better to be fit and fat than

unfit and lean. And exercise is as effective as drugs in treating a range of other conditions, such as depression. What’s more, even a modest weight loss of five kilograms can have very

significant effects on obesity-related risk factors. Perhaps you do think obesity is a disease and exercise is not the right medicine. If you do, be sure to send your obese friends a “get

well soon” card. They may soon be your ex-friends.