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Posted Apr 07 2010 8:10am

A research study in Florida found that rats that were fed junk food developed compulsive eating habits. Does this have implications for humans?

An interesting research study carried out at Scripps Research Institute in Florida has found what its lead researcher – Dr. Paul Kenny – has described as …‘the most thorough & compelling evidence that drug addiction & obesity are based on the same underlying neurobiological mechanisms’.

In the well conducted study there were three groups of rats, each fed a different diet. All three groups had unlimited access to the standard lab food diet. A diet laden with sugar, salt, fat, & of course, calories, including bacon, sausages, cheesecake, & chocolate was fed to one group. Another had access to the same diet, but only for an hour each day. The third group had no access to the junk food diet.

The rats in the first group became so ‘taken’ with the junk food that they were willing to endure painful - but harmless – electric shocks to their feet so that they could eat it. The rats very soon began to eat the junk food compulsively, overeating & becoming obese.

The rats in the second group displayed binge eating type behaviour, consuming sixty six percent of their daily calorie intake from the junk food available to them for the daily hour.

With the use of electrodes implanted in the rats’ brains, the researchers were able to measure their pleasure stimulation & chemical balance. In the group fed only the junk food they found that the rats needed more & more stimulation to release the same amount of pleasure. This indicates that the rats in this group quickly became used to the amounts of junk food they were consuming & needed to continually increase these amounts in order to derive the same pleasure, losing control over their eating behaviour in the process. The parallel with drug addiction – where the addict requires more & more of the drug in order to feel good - is clear. Indeed such behaviour is characteristic of all addictions.

In the UK one in four people are obese & predictions are that by 2020 seven out of ten women & eight out of ten men will be overweight or obese, with a corresponding increase in related health problems of a serious nature - such as cardiovascular disease & diabetes. While additional research is needed to establish how transferable the findings are for humans, it is of undoubted benefit to help understand the underlying effects of reward on food intake. Dr. Kenny pointed out that the research substantiated what obese patients have been claiming for years about how hard it is to stop this sort of eating behaviour. The obvious similarities with drug addiction may indicate possible treatments for addressing obesity.

In the Florida study the altered chemical pathway continued for weeks after the rats no longer had access to the junk food diet. Indeed the rats were initially inclined to do without food rather than return to a normal diet. Further research is required to examine the long-term effects of changing the reward system – it may well be that there is a permanent change in the responses food elicits – which would further help in understanding the complex relationship with food that us humans can have.

In the meantime the evidence from this research presents yet more grounds for eating a healthy balanced diet & encouraging our children to do likewise.

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