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 pounds simply by breathing.
More than 80% of body fat leaves the body through exhaling, making the lungs the primary organ through which we lose weight, researchers say.
Humans have a type of fat in our blood called triglyceride, which consist of three kinds of atoms - carbon, hydrogen and oxygen.
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 22lb (10kg) of fat are fully oxidised, 18.5lb (8.4kg) leaves the body through the lungs as carbon dioxide (CO2). The remaining 3.5lb (1.6kg) becomes water.
The oxygen required for this process weighs nearly three times more than the fat being "lost", so to completely oxidise 22lb (10kg) of human fat, 64lb (29kg) of oxygen must be inhaled, producing 62b (28kg) of CO2 and 24lb (11kg) of water.
The authors, Ruben Meerman and Andrew Brown, said: "These results show that the lungs are the primary excretory organ for weight loss. The water formed may be excreted in the urine, faeces, sweat, breath, tears or other bodily fluids and is readily replenished.
"The exhaled carbon can only be replaced by eating food or consuming beverages such as milk, fruit juices or sugar-sweetened drinks."
At rest, a person who weighs 11 stone (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%, to 240g.
But that can be wiped out by a single 100g muffin, which represents around 20% of an average person's total daily energy requirement.
Professor Brown and Mr Meerman said: "Physical activity as a weight loss strategy is, therefore, easily foiled by relatively small quantities of excess food.
"Our calculations show that the lungs are the primary excretory organ for fat. Losing weight requires unlocking the carbon stored in fat cells, thus reinforcing that often heard refrain of 'eat less, move more'."
The research was published in the Christmas edition of the British Medical Journal.