"No fat people came out of Belsen" is a sentence I never uttered to my overweight patients during my 35 years as a GP.

Instead, I said that weight management was a matter of balance, on one hand the number of calories contained in the food we eat and drink and on the other the number of calories used by the body during the activities of daily living, and by additional exercise.

Even a small number of calories extra to requirements gradually leads to weight gain. I pointed out that a significant effort in the gym is needed to burn off the calories from for example, one chocolate covered digestive biscuit.

I avoided blunt speaking because of the cultural implications and the fact that most of the patients were delightful people.

Like many health professionals, I grew disheartened by the regular visits of (initially enthusiastic) patients whose weight failed to reduce despite the fact that "I really don't eat a lot". My nurse eventually refused to accept people for weight monitoring because it was a waste of time.

Many reasons have been proposed for the increasing weight of our citizens. A tiny proportion of people have medical reasons for weight gain. Some people are better at storing extra calories, which in evolutionary terms provides protection against starving in times of scarcity; others are better at burning them off but it is still a matter of balancing intake and expenditure.

The increased efficiency of agricultural processes has meant a big increase in the availability and variety of carbohydrate foods, cereals, bread biscuits, cakes. Improvements in animal husbandry mean increased quantities of meat and chicken.

Food takes up a lower proportion of the weekly budget than previously, so it is relatively cheaper. Lower ingredient costs mean that it is easier to make a profit from the proliferation of restaurants, fast food outlets and coffee shops.

Children are less active physically, perhaps because of computer games, parental worries about them playing outside and school recreation grounds have been sold off. Schools increase their income by providing vending machines. Why do they need to do that?

The food industry provides more food than people need and the marketing departments have responded magnificently. Few of us can resist the offer of "buy one get one free" and not many can bear to throw away what they do not need. There is a splendid variety of "comfort foods". Who does not recognise the powerful urge to eat for comfort or pleasure? However: "A moment on the lips, a lifetime on the hips." There is no immediate disincentive to indulge ourselves and the consequences only appear years later.

Being overweight is unequivocally related to many adverse health outcomes, especially development of type two(maturity onset) diabetes. This has significant implications for the NHS, as we are reminded almost daily. For example, cash-strapped health authorities face the call to provide "bariatric ambulances" to transport obese people. A telling development is the provision by one local authority of extra-large lairs for the burial of obese people

In the General Election campaign the major parties are vying with each other with promises to support the NHS, but someone has to use the "r" word. Rationing of resources must be acknowledged.

Obesity is a major cost to the NHS and likely to increase. It is reversible by simple, cheap methods: eating less and exercising more. Many overweight people are unable to put this into practice but, unlike most people with what are recognised disabilities, they do have a choice.

As an initial measure I suggest that ambulances should carry scales and height measures. Paramedics would calculate BMI or the assessment tool selected. People over a level judged likely to be hazardous to the wellbeing of those charged with transporting the patient or the safety of the ambulance (guidelines can be developed), should be refused transport.

Do any of our politicians have the stomach for the fight?