Doughnuts are usually off the menu if you're on a healthy eating regime - but Greggs are now offering customers a "diet" version of the sugary treat.

The bakery chain is selling a 'glazed ring doughnut' in addition to its classic 'jam doughnut'.

While the former contains approximately 191 calories, the latter has 245 calories, according to their website.

It appears the introduction of a hole - and lack of filling - has culled more than 50 calories from the sweet favourite.

Greggs is encouraging customers to make the simple swap as part of its new healthier "doughnut diet" initiative.

According to The Sunday Times, it plans to tweak its displays so that jam doughnuts are surrounded by ring doughnuts, guiding the public to order the lower-calorie product.

Speaking at a recent childhood obesity conference in London, Roger Whiteside, Greggs's chief executive said that ring doughnuts "take some of the calories out".

As well as a greater calorie content, jam doughnuts also contain 10g of fat, compared to 6.4g found in ring doughnuts.

However, because of its greater surface area thanks to the hole, ring doughnuts have 13g of sugar — which is 22 per cent of their weight - compared to 12g in the jam-packed alternatives.

Gregg's new campaign is in response to the government's childhood obesity strategy, which is forcing food companies to reduce sugar levels in their products.

Speaking about the challenges the chain faced at the same conference, Whiteside added: "People like big cakes, not little cakes . . . we know that we shouldn't be encouraging people to eat large cakes . . . but the problem is you have to go with demand."

Wendy Baker, a Greggs spokeswoman, told the paper that they were "serious about customer health".

She added: "A wider choice of ring doughnuts has been introduced which range from 190 to 260 calories, compared to traditional fondant doughnuts which range from 225 to 340 calories.

"Greggs has also reduced sugar by 20 per cent across its sweet range."

-This article first appeared on Yahoo