People have remarked in recent years that obese individuals behave like drug addicts. A new study by the University Bordeaux has shown that sweets are infact addictive. And surprisingly, more addictive than cocaine. Both act on the brain’s dopamine reward system and tend to induce addictive traits in users.

But don’t start railing lines of sugar. I’ve heard it causes a terrible headache. More details on the study after the jump.

Rats who had never been exposed to refined sweetness (sugar and saccharin) or cocaine were placed in an environment and chose 8 times a day between two mutually exclusive levers. One lever dispensed intravenous cocaine while the other granted access for 20 seconds to saccharin sweetened water. Before making their choice rats were allowed to sample each lever twice to ascertain their rewards. Three reward conditions were set up. One group of rats was rewarded only when the cocaine lever was pushed (pushing the saccharine lever did nothing). It took on average 11 days for these rats to show preference for the cocaine lever. Another group was rewarded only when the saccharine lever was pushed. These rats showed preference after 7 days.

The last group was rewarded for either lever (if the cocaine lever was pushed, cocaine was dispensed. Similarly for the saccharine lever). Surprisingly, when given the option of both substances, these rats developed a preference for saccharine after only two days. Even more surprisingly is that the rats took full advantage of their sample period. The rats sampled the cocaine lever before their choice almost maximally after day 7, showing that they were aware of the reward from the cocaine lever. Despite constant cocaine sampling the rats still chose the saccharine lever after the sampling.

The sampling of saccharine water over cocaine was not due to thirst, as rats preferred cocaine over plain water every time. The preference for saccharine over cocaine was also not due to a low dosage of cocaine. The study ran trials where cocaine dosage was increased, up to the maximal dosage for rats (anymore would cause convulsions). Despite incredibly large cocaine doses, rats still preferred saccharine.

Despite being intravenous, cocaine still takes several seconds reach the brain and its effects fully felt. Tasting saccharine is near instantaneous. It was theorized that this immediate reward may contribute to the preference. To test this, the saccharine lever only delivered the reward after a small pause (0-18s) while keeping cocaine delivery constant. Again, rats preferred saccharine, even when the pause was many times greater than cocaine.

The study even tried to test the “price” for the reward. The number of times the saccharine lever must be pushed before the reward is delivered was varied. An increase anywhere from 2 to 8 lever-pushes per reward did not affect the preference and in fact strengthened the desire for saccharine.

Lastly, rats trained with the cocaine-only reward environment were placed in the saccharine/cocaine environment. These rats had previously developed a stable preference for cocaine. These rats rapidly changed their preference to saccharine. Finally, the study placed high-exposure cocaine rats (6 hr/day of self-administration for three weeks) into a saccharine/cocaine reward environment. Even these coked out rats rapidly changed their preference to saccharine.

It is quite clear that saccharine is a much stronger drug than cocaine in rats. Almost all rats preferred saccharine over cocaine, even if they had a preexisting and strong addiction to cocaine. Increase in cocaine dosage, saccharine reward price, sensitivity and tolerance did not affect the preference for saccharine. The tests were repeated with sugar to be certain the zero-calorie attribute of saccharine was not the cause. The results were identical to saccharine.