Do people who take weight loss pills eat unhealthily?

"Are slimming pills fuelling the obesity epidemic?" asks the Mail Online, reporting on research that suggests dieters "mistakenly believe they can eat whatever they want" after taking weight loss drugs.

There is nothing in the research to prove the Mail's headline. In fact, its headline was prompted by US experiments on the effects of marketing a weight management treatment as a "drug" or a "supplement".

The research looked at whether the difference would change healthy lifestyle beliefs and behaviour, and whether this is influenced by knowledge about weight remedies and nutrition.

Researchers found that when people were shown an advert for something marketed as a drug, it led to them eating more cookies (an unhealthy behaviour) than when the same treatment was advertised as a supplement.

They further found giving people more knowledge about weight loss remedies was more effective at mediating this unhealthy eating than giving them more knowledge about nutrition in general.

Very limited conclusions can be drawn from this study, and it does not provide evidence that taking weight loss treatments encourages unhealthy lifestyle behaviours, or that these remedies make people think they can eat what they want. These experiments were very specific one-off scenarios in relatively small samples of young adults.

Most importantly, this US study has little bearing in the UK, where drugs are not marketed to the public. Prescribed weight loss treatments have a specific set of criteria controlling their prescription.

This study is not conclusive. We don't know whether – and how – taking weight loss drugs directly influences people's beliefs about health and nutrition.

Where did the story come from?

The study was carried out by professors of business and marketing from three business schools in Philadelphia and New Hampshire, in the US.

Financial support was provided by the Collaboration to Reduce Disparities in Hypertension (CHORD) project funded by the Pennsylvania Department of Health, and from the Ackoff Fund of the Wharton Risk Management and Decision Processes Center.

The study was published in the peer-reviewed Journal of Public Policy and Marketing.

The Mail's conclusion that, "dieters using slimming pills mistakenly believe they can eat whatever they want" cannot be made based on this set of experimental studies, which have limited application to the situation in the UK.

The study also provides no evidence that slimming pills are fuelling the obesity epidemic.

What kind of research was this?

This was an experimental study conducted in the US. It explored the impact of the marketing of weight management remedies on healthy lifestyle behaviours. These remedies are described as covering "products or services designed to reduce risk and offer solutions to challenges consumers face".

The researchers investigated three main questions:

• How does marketing of weight management remedies (specifically, the marketing of products labelled as drugs versus those labelled supplements) affect actual healthy behaviour?
• Is the impact of weight management remedy marketing rooted in erroneous beliefs about remedies themselves? Or is the impact of weight management remedy marketing more driven by the consumer's choice between remedies (such as drugs versus supplements)?
• Previous research has not specifically tested the impact of "health literacy" on consumer response to weight management marketing. The researchers wanted to investigate the impact of two critical dimensions of health literacy: "nutritional knowledge" and "remedy knowledge".

The researchers conducted three experiments examining these questions, which were centred on their three theories.

What did the research involve?

Study one: how weight management remedy are marketed

The researchers believed there is a difference between the marketing of drugs and supplements. They say supplements have less association with poor health, and remind consumers of the importance of other health-protective behaviours.

On the other hand, marketing something as a drug treatment could undermine, rather than enhance, healthy lifestyle behaviour. So their first theory is that, "actual unhealthy decisions and behaviour will increase after exposure to weight management drug marketing, but decrease after exposure to supplement marketing".

This first study investigated the impact of drug and supplement marketing on food consumption behaviour. They divided 138 young adults (average age 22, made up of university staff, students and other residents of the area) into six groups and exposed them to either a drug or supplement remedy message, or a no-remedy control message. They then gave them the opportunity to consume a product framed as either relatively unhealthy or healthy (via an explicit low-fat cue).

Both the drug or supplement and no-remedy message started with the line, "Avoid fatty foods and follow a sensible eating plan. This is the only way to achieve an overall healthy lifestyle." The no-remedy message ended there.

The other two added an advertisement about a weight loss treatment that stops fat being absorbed, which was described as being either a FDA-approved drug or a supplement.

Participants were then given free access to cookies, either described as being low-fat and guilt-free, or delicious and indulgent. Participants also completed questions on their views and attitudes.

Study two: how health literacy affects people's response to marketing

The second study examined health literacy. It looked at how knowledge of nutrition and remedies influenced people's response to marketing of remedies. This was to test their theory that, "Remedy knowledge will be more effective than nutrition knowledge at mitigating the negative impact of remedy marketing on healthy lifestyle decisions and behaviours".

The researchers included 356 participants, who they recruited online for a financial inducement. Each group read a short scenario describing the weight management treatment of an individual in a clinical trial. One group were told that he was given a drug or supplement, one was told he chose to have the drug or supplement, and the third group were told he was given a placebo.

Participants were then asked to rate on a scale the likelihood that the individual in the scenario would "follow a low-fat diet", "eat healthy foods", and "live a healthy lifestyle". Participants also rated the individual's likely motivation and effectiveness of the treatment. They then completed questionnaires assessing their remedy knowledge and nutrition knowledge.

Study three: how understanding of nutrition and remedies affects healthy decisions

The third study looked at the impact of information on actual health choices in the presence of weight management marketing.

In this study, 129 young adults (average age 20, again university staff, students and residents) read two articles compiled from Wikipedia, one focused on remedies and one focused on nutrition. They manipulated knowledge by providing information that would have varying relevance to healthy consumption behaviour.

For the "high-remedy knowledge" group, the article contained information about drugs and supplements, including how they support health. For the "low remedy knowledge" group, the article contained less information on health.

For the "high-nutrition knowledge" group, the article included World Health Organization (WHO) information on dietary health, including how to promote health and reduce risk. For the "low-nutrition knowledge" group, the article contained less information relevant to health.

Participants rated the readability and interest in the articles. They then looked at the advertisement for the same weight loss remedy as used in study one, which was described as a drug for all groups. They were then offered their choice of a relatively healthy snack (a strawberry) or a relatively unhealthy snack (a Lindt dark chocolate truffle).

What were the basic results?

Study one: how weight management remedy are marketed

As the researchers expected, perceptions of the remedy as a "drug" were significantly higher when the same treatment was described as a US Food and Drug Administration-approved drug, rather than a supplement. Also, as expected, participants rated the same cookie as healthier when it was labelled as being "low-fat".

When the researchers analysed the interaction between different forms of marketing of the remedy and the cookie, they found some significant interactions. In particular, they found people who had seen the drug message ate significantly more cookies than those who had seen the supplement message and those who had not been given a remedy message.

Those who had seen the drug message also ate more cookies described as regular than low-fat. Meanwhile, those who had seen the supplement message ate significantly fewer cookies than those who had seen no remedy. Their consumption of cookies described as low-fat was also marginally, but not significantly, higher than those seeing no remedy.

Study two: how health literacy affects people's response to marketing

The researchers found that regardless of whether people were told the remedy was assigned to or selected by the subject, they expected his healthy lifestyle choices to be lower for a drug than a supplement.

In fact, when the researchers compared this with the control group, who were told the individual was taking a placebo, expected lifestyle ratings were no different than when told they were taking a supplement, but significantly less when told they were taking a drug.

Perceptions of motivation were found to mediate the effect of the remedy on lifestyle behaviour (for example, higher levels of motivation decreased the negative impact of the drug on lifestyle).

Study three: how understanding of nutrition and remedies affects healthy decisions

People with lower-remedy knowledge were more likely to choose the unhealthy snack compared with people with high-remedy knowledge. Nutrition knowledge had no significant effect on choice of snack, though unhealthy choices were more frequent with higher versus lower nutrition information.

How did the researchers interpret the results?

The researchers concluded that the three studies "demonstrate that exposure to drug (but not supplement) marketing for weight management encourages unhealthy consumer behavior, due to consumers' reliance on erroneous beliefs about health remedies".

When further exploring the possible mitigating role of health literacy (nutrition knowledge and remedy knowledge), they concluded that, "Remedy knowledge is more effective than nutrition knowledge at lessening the effect of weight management drug marketing on unhealthy behaviour".

Conclusion

This series of three experiments has investigated the effect that marketing a weight management treatment as a "drug" or a "supplement" has on healthy lifestyle beliefs and behaviour.

It also investigated whether people's understanding of health, in particular knowledge about weight remedies and nutrition, influences this.

The researchers found that believing something is a supplement encouraged "healthier" choices, rather than when people were told the same treatment was a drug. Their second experiment further suggested that weight management drugs undermine a healthy lifestyle by reducing motivation to engage in healthy behaviours.

They then found clues to suggest that knowledge of weight loss remedies mitigates effects on a healthy lifestyle – people were less likely to choose an unhealthy snack when they had been given more knowledge about the treatment. However, increased knowledge about nutrition didn't affect the healthy food choice.

This is an interesting study, but very limited conclusions can be drawn and it does not provide evidence that taking weight loss treatments encourages unhealthy lifestyle behaviours, or makes people think they can eat what they want.

These experiments were three very specific and one-off scenarios that may have very limited relevance to the real life situation. For example, in the first study, people were only shown an advertisement of a treatment marketed as a drug or supplement and were then offered a plate of cookies. They didn't actually take this treatment.

It is difficult to understand how just looking at an advertisement for a treatment you are not taking would directly cause you to eat fewer cookies just because you saw it called a supplement rather than a drug.

Given the large number of analyses that the researchers conducted, looking at interactions between a range of different scenarios, it could be possible that some of these findings may not show true cause and effect (causative) associations.

For example, in the first study, there were relatively small sample sizes in each group when they are broken down into the different remedy and food marketing conditions.

There was also no description of any attempt to ensure each group of adults was matched in terms of their usual eating habits, so any difference seen between the amount of cookies each group consumed may not be solely attributed to the messages they had just read.

But, most importantly, this study was done in the US and therefore has very limited applicability to the UK situation. Drugs are not marketed to the general public in the UK as they are in the US. Prescribed weight loss treatments are not advertised and have a specific set of criteria controlling their prescription.