A closer look at coffee research shows little evidence of significant weight loss from switching to Coffee Slender. (Photo: Eivind Nicolai Lauritsen)

Evidence is slim for Coffee Slender’s claims

The research results don’t back up the product’s marketing promises of rapid weight loss just by switching your brand of coffee.

In a world where half the population is overweight, who doesn’t want to find an easier way to lose weight - or at least avoid gaining it?

Can it really be as simple as drinking a special coffee? According to Immitec, who sells the dietary supplement Coffee Slender, it is.

It's almost too good to be true, writes Immitec in its advertising. Quoting from their literature, they assure us that they have scientific documentation to support this claim:

“In 2002, an open pilot study was conducted on our coffee extract Svetol at The University of Maine, USA. […] 60 per cent of the respondents had a 50 per cent decrease in their blood sugar. Reduced blood sugar means less insulin and less storage of fat in the body.”

And a 2007 Norwegian double-blind study showed that individuals who consumed Coffee Slender lost an average of 5.4 kg over 12 weeks.

So it works, right?

Not exactly. A closer look at the coffee research shows that switching to Coffee Slender is not going to help anyone lose much weight. Even Erling Thom, the researcher behind the 2007 Norwegian study, admitted to forskning.no that the effect of the active substance is minimal.

So why has Coffee Slender then become the latest big weight loss fad?

Chlorogenic acid

According to the science, drinking coffee to avoid overweight isn’t necessarily a bad idea.

Numerous studies, including one from 2016, indicate that ordinary coffee can have a positive effect both on one’s weight and on one’s risk of diabetes over time, albeit a very small one.

The difference may amount to one or two kilos between coffee drinkers and non-coffee drinkers.

So is it possible to increase the effect by consuming more?

Caffeine is just one of several substances in coffee. It is a stimulant and large doses have a number of adverse side effects. This limits its weight-loss potential.

Another substance in coffee is chlorogenic acid, which is found mostly in green coffee beans. Roasting the beans reduces the amount of chlorogenic acid, but some still remains in the coffee you drink.

Animal research has suggested that chlorogenic acid, or green coffee extract, may have some weight-loss effect. This is the idea behind Coffee Slender, which has a much higher chlorogenic acid content than regular coffee.

But does it work?

Limited studies cited

Immitec says yes, and refers to the pilot study and the Norwegian study of 30 Norwegian patients in 2007, which found that patients who consumed Coffee Slender lost over five kilos and had a lower percentage of body fat than those who drank regular coffee.

Several more recent studies paint a less optimistic picture, and Immitec Chairman Jan Oddvar Johansen gives no clear answer as to why the company cites only the two named studies.

“We’ve taken over this product since we acquired Med-Eq. The product developers paid for the studies, and they were carried out before our time. I don’t know how the studies were financed or conducted,” he said..

Immitec acquired Med-Eq, a supplier of food supplements, in 2014. But the company still references the Norwegian study in its marketing of Coffee Slender on its website.

Later studies are not mentioned.

Poor studies

Already in 2011, Igho Onakpoya and his colleagues at the University of Exeter in the UK summarised chlorogenic acid research on humans.

Their summary evaluated the Norwegian study and two other studies. Each of the three studies concluded that the drug has a slimming effect, but the authors cite major weaknesses in the studies:

The small number of study participants means that coincidences can easily arise and colour the results.

The short-term nature of the studies means we have no idea what happens if individuals use green coffee extract supplements for longer than three months.

In one study, two of the authors have leading positions in the firm that markets the drug- and a vested interest in advantageous product results, which can affect the research process.

The second study cannot be found in any journal, so there is no guarantee that it has gone through any independent scientific assessment.

And only one researcher carried out the Norwegian survey, which is a questionable practice for this type of study. It is difficult to conduct double blind clinical trials properly when working alone.

The quality of the three studies is poor. The effect of chlorogenic acid is small. All in all, Onakpoya and his colleagues conclude that the effects and side effects of chlorogenic acid are very uncertain.

Chlorogenic acid not recommended

Researchers Rachel Buchanan and Robert D. Beckett arrived at the same conclusion in 2013, in a summary published in the Journal of Evidence-Based Complementary and Alternative Medicine.

They wrote, “Despite the potentially clinically significant weight loss achieved in some published studies, all held significant limitations. Green coffee extract is not recommended as a safe or effective treatment for weight loss.”

Heather Hausenblas and Brianna Huynh write in a similar vein in a summary published in the Natural Medicine Journal in 2014.

The authors behind a 2016 review of many different dietary supplements for weight management also do not recommend the use of chlorogenic acid.

No miracle cure

The sad truth is that no one has come up with any effective weight-loss product yet.

Despite all the headlines about the new miracle cures over the last few decades, the treatment of overweight and obesity poses an ever greater challenge.

Even pharmaceutical companies, with all the economic and research-related weight they exert, have struggled to find useful drugs against overweight and obesity.

To date, even the effect of prescription diet pills has been modest, and numerous drugs have been taken off the shelves due to serious side effects.

So there’s good reason to be wary when advertisements for weight-loss supplements pop up. Even when they claim to have scientifically documented effects.

It often is too good to be true.


Read the Norwegian version of this article at forskning.no

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