Food scientists working for fast food and sweet manufacturers like Nestlé and Unilever revealed that the food industry had known for years that its products undermined the body's ability to regulate intake and lead to obesity, and are now searching for a solution. One scientist expressed his fears that they had created "a bio-chemical monster" .

This 'overeating effect' was attributed to chemical opioids in the products, which both produce a desire to eat more and reduce the 'full' feeling which kills appetite. The effect appears to be strongest in products high in both saturated fats and carbohydrates, like chocolate-flavoured breakfast cereals, cheesy savoury snacks, hamburgers and cheeseburgers (where buns with added sugar are used). The Food Industry denied that any proven effect had been shown, but lawyers currently involved in class actions against the Tobacco Industry (claiming negligence on the grounds that the Industry knew but never admitted or publicised nicotine's addictiveness or the links between smoking and cancer) were showing interest.

A recent review of the last 20 years' research into the effects of food opioids concluded that people tended to eat a fifth less if they had been given an opioid-suppressing drug before the meal. In obese people appetite could be reduced by a third (Yeomans,MR & Gray,RW. Neuroscience and Biobehavioral Reviews 2002;26:713-28).