“Cocaine users 'thinner' because drug alters metabolism,” The Independent explains.

The illegal stimulant cocaine has long been known to have appetite-suppressing properties. But a new study suggests it may also alter the way the body responds to fat intake.

The study in question compared 35 men who were cocaine dependent with 30 healthy men who were non-drug users – with particular focus on their dietary habits and body composition.

It found that the cocaine users had behavioural habits normally associated with weight gain, such as eating lots of energy-rich fatty foods and drinking more alcohol. But despite these behaviours, the cocaine users had less fat mass than non-users.

The findings suggested that cocaine use may lead to the body storing fat differently.

However, there are a number of limitations. This small study only assessed diet once, it did not assess how physically active the men were which may also affect their fat mass, and the results may not be applicable to more diverse groups of cocaine users.

Overall, this study is of interest to those studying cocaine addiction and its effects – weight gain after quitting the drug can often be a cause of relapse. But the findings should not be seen as an advertisement for Class A drug use to reduce body fat – there are far safer, and legal, ways to lose weight.

Where did the story come from?

The study was carried out by researchers from the University of Cambridge and Cambridge University Hospitals NHS Foundation Trust. It was funded by the UK Medical Research Council.

The study was published in the peer-reviewed scientific journal Appetite and has been published on an open access basis so it is free to download.

The Independent and the Mail Online cover the study reasonably.

What kind of research was this?

This was a cross sectional study looking at the reasons behind the weight loss associated with cocaine use.

Cocaine is widely believed to have appetite suppressing properties, and weight gain may occur when it is no longer used.

Despite losing weight, cocaine users report fewer balanced meals and preferring fatty foods. The researchers wanted to see if factors other than appetite might contribute to the drug’s influence on weight.

What did the research involve?

The researchers compared 35 men who were cocaine dependent with 30 healthy men who were not drug users. They looked at their eating and dietary habits, their body composition, and their levels of the hormone leptin that helps to regulate food intake and body weight.

The male drug users were diagnosed as being cocaine dependent using standard criteria. They were not seeking treatment for their dependency, and were actively using the powder (40%) or freebase (smokeable) form (60%) of cocaine.

They had been using the drug for an average of about 15 years. Most of the men were also dependent on other substances, such as nicotine (91%), opiates (43%), and alcohol (29%). Most of those who were dependent on opiates were prescribed methadone (31%) or buprenorphine (9%). The non-drug users had to have no history of substance misuse disorders themselves or in their families, and they all tested negative for illegal drugs on a urine test.

The men’s diets were assessed using the tried and tested Food Frequency Questionnaire. They also completed another questionnaire assessing their eating behaviour tendencies:

restrained eating (deliberate restriction of food intake to control body weight)

uncontrolled eating (tendency to eat more than intended by losing control over food intake)

emotional eating (tendency to eat in response to emotional cues)

They also had their body mass index (BMI), waist-to-hip ratio, skinfold thickness, fat mass, non-bone lean mass, bone mineral density, and leptin levels measured.

When comparing the men’s diets they took into account differences between groups in food and alcohol intake, smoking status, and medication use (potential confounders). They also analysed men who used opiates separately to see if this affected results.

What were the basic results?

The cocaine users had spent less time in education than non-users, and had more impulsive and compulsive traits. None of the cocaine users reported using cocaine for its weight loss or appetite suppressing effects (researchers say that this is a common finding in male cocaine users).

Eating habits

Compared with the non-users, the cocaine users reported:

higher dietary fat, carbohydrate, alcohol, and calorie intake

lower sugar intake

skipping breakfast more frequently

uncontrolled eating patterns

These differences were statistically significant even when potential confounders were taken into account.

Body weight and fat levels

The following results were reported:

there was no difference between cocaine users and non-users in BMI or waist-to-hip ratio

the cocaine users weighed on average about 6kg less than the non-users,

the cocaine users also had less fat mass relative to lean mass on body scans than non-users

leptin levels were not significantly different between cocaine users and non-users

On this last point, lower levels of leptin were seen in individuals with lower BMI among both the cocaine users and non-users. In cocaine users leptin levels also appeared to be lower the longer the men had been using the drug.

How did the researchers interpret the results?

The researchers concluded that their findings “challenge the widely held assumptions that cocaine use leads to weight loss through a global suppression of appetite”. Instead, the findings suggest that cocaine users lose weight because of changes in how their bodies store fat.

They suggest that when people stop using cocaine the effect on fat regulation may produce significant health problems that are currently likely to be overlooked.

Conclusion

This study suggests that despite taking in more calories, and eating more fat and carbohydrates, cocaine users have a lower fat mass than non-users. The researchers suggest that this shows some underlying difference in how their bodies process fats, possibly due to lowered levels of leptin, rather than having a reduced appetite.

There are some points to note when interpreting these findings:

The researchers did not assess the men’s physical activity to see if this could account for the cocaine users’ reduced fat mass. They suggest that as the cocaine users’ lean mass (which includes muscle mass) was not higher, then physical activity was unlikely to be solely responsible for the reduced fat mass. However, as cocaine is a stimulant, levels of physical activity should be assessed to identify what effect it could be having.

The study was cross sectional, therefore it cannot tell us what the men’s eating habits or body compositions were before they started using cocaine. It also doesn’t tell us what happens when they stop using the drug.

It does not show that leptin is responsible for the changes seen as the level of leptin did not differ significantly between the two groups.

The single assessment of diet may not reflect the men’s diets over a longer period. Despite eating more, it is also not clear whether cocaine use has any effect on food absorption – for example, cocaine can cause constipation, and use of laxatives (which reduce food absorption) was not assessed.

The study was relatively small, included only men, and they had a relatively long history of cocaine use (an average of 15 years). The findings may not be representative of the wider population of cocaine users, particularly women.

It is important to note that the men who used cocaine did not have different BMIs or waist to hip ratios, which are the commonly used measure of body-fatness.

Therefore they may not appear to be “skinnier” than their counterparts. Also, despite having less fat mass, whether they have any reduction in the longer term cardiovascular outcomes was not assessed, and other effects of their drug use may counteract any potential “benefit” this reduction may have.

Overall, this study is of interest to those studying cocaine addiction and its effects, but should not be seen as an advertisement for drug use to lose weight.

Previous generations of ‘diet pills’ were essentially nothing more than stimulant drugs, similar to cocaine, such as amphetamines. These proved to be both addictive and have potentially harmful side effects.

Analysis by Bazian

Edited by NHS Website