LONDON (Guardian) - Supersized chocolate bars and "grab bags" of sweets are to be banned from hospitals in Britain as the National Health Service ratchets up its fight against obesity .

Mr Simon Stevens, the NHS chief executive, has warned that obesity will bankrupt the health service.

Shops inside hospitals have stocked sugary drinks, sweets and unhealthy snacks, which have been bought not only by patients and their visitors but also by NHS staff.

Nearly 700,000 of the NHS' 1.3 million staff are estimated to be overweight or obese.

Mr Stevens has instructed all hospitals not to allow any confectionery on the shelves that contains more than 250 calories.

Also out are "grab bags", which are theoretically to share or save.

Mr Stevens' edict will force hospitals to ban them because the contents, which could be consumed by one person in one go, contain far more than 250 calories.

The NHS has already taken action that campaigners hope to see in the government's anti-obesity strategy for the whole country.

Price promotions have been banned, as has advertising of unhealthy foods on NHS premises.

Healthy options are supposed to be available at all times for patients, visitors and staff.

As part of the crackdown, leading retailers including WH Smith and Greggs agreed in April that no more than 10 per cent of their soft drink sales would be high in sugar.