Cocaine might not suppress appetite after all


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Why are chronic cocaine users so skinny? Scientists have always theorized that the drug suppresses the appetite. Individuals in rehab often gain a significant amount of weight, which many assumed was a result of patients substituting food for drugs. A new study from the University of Cambridge contradicts all of that. 

Published in the journal Appetite, the study found that cocaine affects the metabolism in a way that prevents the user from gaining weight and storing fat. Once the user quits taking the stimulant and the drug is no longer changing their metabolism, they gain weight. 

Weight gain can make it harder for patients to stay clean, and this new research suggests the earlier the intervention, the less of a chance of drastic weight gain, improving the person's chances of recovery. 

"Our findings challenge the widely held assumptions that cocaine use leads to weight loss through appetite suppression. Rather, they suggest a profound metabolic alteration that needs to be taken into account during treatment," said Karen Ersche, from the Behavioural and Clinical Neuroscience Institute at the University of Cambridge. 

Researchers analyzed the body composition, diets, eating habits and levels of leptin — a hormone that plays an important role in regulating appetite and energy use — in more than 60 men. Half of the men had a dependency on cocaine, while the other half (the control group) had no personal or family history of drug abuse. 

The cocaine users preferred foods packed with fat and carbohydrates and showed patterns of uncontrolled eating. Despite this, they typically lost weight while using cocaine, and their body fat was significantly reduced compared to the control group. Their leptin levels were low, and there was an association between the levels and how long they had been using. 

According to the press release, "a decrease in plasma leptin together with a high-fat diet suggests an impaired energy balance, which typically leads to weight gain rather than weight loss."

Because of the drug's effect on cocaine users' metabolism, their poor eating habits went unnoticed while they were using — their weight and fat content weren't reflecting their diets the same way weight and fat content reflect the diets of typical non-users. 

But when they quit cocaine, they gain weight because they're still eating poorly, but the drug is no longer changing their metabolism.

"We were surprised how little body fat the cocaine users had in light of their reported consumption of fatty food. It seems that regular cocaine abuse directly interferes with metabolic processes and thereby reduces body fat. This imbalance between fat intake and fat storage may also explain why these individuals gain so much weight when they stop using cocaine," Ersche said.