A study at the Scripps Research Institute in Florida has found that Junk food may be as addictive as cigarettes and heroin.

The study used rats who were fed a junk food diet of bacon, sausages and cheesecake. The rats began to gain weight, obviously, but they also showed the tell tale signs of food addiction. During the study the rats lost all sense of sensible eating behaviour and they began to gorge themselves on the junk food even when they were full.

The rats even over-ate when they anticipated receiving electric shock treatment to their feet if they ate high fat junk food. Other rats eating a normal non high fat diet were rewarded by receiving pleasurable electric stimulation when they refused the junk food. But scientists studying the rats eating the high fat diet found that these rats simply refused to eat nutritious food.

The researchers found that those rats who ate high fat junk food had altered chemicals in the brain that didn't allow them to make choices that equalled reward rather than punishment. Other studies have shown that the same thing happens when rats are given heroin or cocaine, suggesting that eating junk food is as addictive as class A drugs.