Obesity could be triggered by 'pleasure mechanisms' similar to those involved in drug addiction.
People who are struggling to keep their weight down may be reassured that they could be facing an addiction similar in strength to those experienced by drug addicts.
A study in the US looked at the habits and behaviour of rats which were given access to junk food and found a deterioration in the chemical balance involved in the brain circuits which was very similar to that of drug users.
In a press statement, one of the researchers said: "It presents the most thorough and compelling evidence that drug addiction and obesity are based on the same underlying neurobiological mechanisms."
He added that the rats "completely lost control over their eating behaviour", demonstrating typical signs of addiction.
A body mass index of 25 or over is classed as obese and has various serious health risks, including an increased chance of developing heart disease.