It will be a huge sigh of relief for anyone who sneaks in that naughty extra mince pie this Christmas – scientists have discovered you can shed the kilos simply by breathing.

More than 80 per cent of body fat leaves the body through exhaling, making the lungs the primary organ through which we lose weight, researchers say.

Shedding unwanted fat requires unlocking the atoms in triglyceride molecules through a process known as oxidation.

Scientists at the University of New South Wales in Australia found that when 10kg of fat are fully oxidised, 8.4kg leaves the body through the lungs as carbon dioxide (CO2). The remaining 1.6kg becomes water.

More than 80% of body fat leaves the body through exhaling

The oxygen required for this process weighs nearly three times more than the fat being ‘lost’, so to completely oxidise 10kg of human fat, 29kg of oxygen must be inhaled, producing 28kg of CO2 and 11kg of water.

At rest, a person who weighs 70kg exhales around 200ml of CO2 by taking 12 breaths a minute. So by breathing out 17,280 times a day they will lose at least 200g of carbon, with around a third of that weight loss achieved during eight hours of sleep. But to keep the weight off requires putting less back in through eating than is exhaled by breathing – which might be tricky come that second turkey sandwich on Boxing Day.

Going for a run for an hour would help remove an additional 40g of carbon from the body, the researchers say, raising the total loss by around 20 per cent, to 240g.

But that can be wiped out by a single 100g muffin, which represents around 20 per cent of an average person’s total daily energy requirement.