McDonald's cheeseburger left in doctors' surgery for 2 YEARS - can you guess what happens to it?

Two chiropractors in Michigan left a sandwich and a chicken taco on the counter of their surgery to make people think about what they are putting into their bodies

 Dinnertime: The two-year-old cheeseburger seems mostly unchanged

What happens when you leave a McDonald's cheeseburger unattended in the open air for two years?

The answer is nothing, really. No mould, nasty smells or ants.

It just sits there uneaten as people walk past.

Fast food: The taco and the burger seem quite close to edible, thanks to preservatives

Two chiropractors in Waterford, Michigan, US, left the sandwich and a Taco Bell chicken taco on the counter of their surgery to see what would happen to them.

Dr Jacqueline Vaughn hopes it will make people think about what they are putting into their bodies every time they make a trip to their local fast food restaurant.

Over almost two years, the meals appear unchanged - apart from the cheese on the burger turning a darker brown and the taco's lettuce greying slightly.

"There's no smell from it, it's basically mummified. You can pick it up, turn it over and still see the cheese and pickle in the burger ," Dr Vaughn told.

"Even in the summer when we get ants, the bugs won't go near it."

Dr Vaughn says she intends to leave the fast food on display "forever", although anyone expecting a dramatic transformation will most probably be disappointed.

The beginning: A fresh McDonald's cheeseburger

Yafan Zhang, professor of food science at Wayne State University, says a preservative called calcium probinate keeps the food looking near-edible for a long time.

He told the non-toxic substance is used in a range of products to keep them fresh, including bread, cakes and processed meat.

The product is safe to use and eat. Although it can sometimes cause inflammation of the stomach, it is fine unless it is eaten every day.