Chocolate can create same high as opium

It’s certainly a good excuse to have when you’re slumped on the sofa and feel like you're simply obliged to finish off that shiny tin of Quality Street.
Chocolate has an effect on the brain similar to opium, according to a study that found amazing comparisons between obese people and drug addicts.
In the study, a natural brain chemical called enkephalin - an endorphin with similar properties to opium - surged as rats began to eat M&M chocolates. When a drug was used to stimulate the dorsal neostriatum - the brain area releasing the chemical - the number of M&Ms eaten more than doubled. In the brain, enkephalin binds to molecular ‘receptors’ sensitive to opiate chemicals to reduce pain and produce pleasurable feelings.

Source  - Daily Mail