Should the NHS pay for operations for people with diseases caused by unhealthy lifestyles?

In some parts of the UK, obese people have been refused treatment for any ailment at all until they lose weight. It is mooted that smokers should not be given treatment for lung or mouth cancer unless they give up smoking - some say they should not be treated at all because the disease is their own fault. Smoking is clearly an avoidable action, but in the case of obesity, perhaps it is more complicated. Some people eat very unhealthily, and yet do not put on weight - under those strictures if they got heart disease from eating too much trans fats they would be treated by the NHS. An obese person may eat relatively more fruit and vegetables and less fat, but because they are visibly overweight be denied the treatment. Sometimes the cause of obesity is linked to a mental health problem - such as being brought up during austerity - a war, for example - and learning to eat food when it was available or face starvation - a strategy that doesn't work so well in times of plenty. Or, they were taught through the actions of their parents or carers that food is a way of showing love. Many overweight people would like to lose weight, but struggle to do so for any amount of time. Some have slow metabolisms. They should not be punished for their body type or circumstances.