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A fat burning supplement: fat or fiction?

A popular nutrition supplement with claims to help weight loss and fat burning is the seaweed extract fucoxanthin. Let's explore these claims in further detail...

Sport science exercise nutrition


Sometimes it is the sole ingredient in a supplement and sometimes it is combined with a range of other ingredients. From web sites you can learn that “fucoxanthin has been clinically shown to promote weight loss, reduce body fat and trim waist and hip circumferences”. Often a number of other benefits are listed as well. So should we all run to the store and stock up on this supplement? Perhaps this would be a little premature. If you read a little further on those web sites, you can sometimes find in a smaller font that “These statements have not been evaluated by the Food and Drug Administration”.

A look at the evidence

Let's have a look at where these claims come from and what the evidence REALLY is. Fucoxanthin is a carotenoid found in edible brown seaweeds (Undaria pinnatifida). In animal studies it has been demonstrated that long term fucoxanthin supplementation can result in weight loss. For example, a study by Japanese researchers Maeda and colleagues demonstrated that fucoxanthin (or an extract that contained fucoxanthin) resulted in a significant reduction in fat tissue (white adipose tissue) in mice after 4 weeks.

The underlying mechanism

When such findings are reported it is always important to ask about the causes of the effects. What is the underlying mechanism by which the supplement has the observed effect? In this case it was suggested that one of the potential mechanisms was “an upregulation of mitochondrial uncoupling protein 1 (UCP1)” which would result in an increase in resting energy expenditure. This sounds expensive, but essentially means that your body is more wasteful with energy. This implies that you will expend more energy without extra effort. Of course when you want to lose weight and want to expend more energy than you ingest, this would be a good thing. The explanation seems plausible. So far, so good... There is an interesting finding and a plausible mechanism (with a little bit of support for this mechanism as well).

It is always important to ask about the causes of the effects

From cells and animals to humans

So the next step is to ask questions about how the experimental model that was used translates to a human real life situation; the study was not performed on humans but it was performed with mice. It is well know that rats respond very differently to different diets and have very different fat metabolism than humans. So at the very least one should be very cautious when extrapolating the findings of an animal study to real life human situations, especially when it concerns fat metabolism.


When reading the article more carefully, you will find that the amount of the supplement that was given to these animals was 0.4% of the animals body mass. A quick calculation would reveal that 0.4% body mass of a 70kg human would equate to 280g of fucoxanthin per day. Clearly this would be considered a totally unrealistic dose. A fucoxanthin supplement that you would buy would contain 300 milligrams, or roughly 0.1% of that 280g dose. In other words: to ingest that amount, you would need to take in a 3 year supply of the supplement in one go! This would be using a concentrated form of the substance that can be found in normal foods, in this case seaweed. If the required amount of fucoxanthin were to be consumed as real food, one would have to eat two thirds of their body weight in seaweed. For our 70 kilogram (154 lbs) person this would be 53.3 kilograms (118 lbs) of brown seaweed!

To ingest that amount, you would need to take in a 3 year supply of the supplement in one go!

Are there any human studies?

Are there any published human studies? Well, there is one. A Russian study was published that used fucoxanthin for the first time in humans. In this study, the effects of a product were investigated that contained brown marine algae fucoxanthin as well as pomegranate seed oil. Daily administration of 600 milligrams of an extract that contained 2.4 milligrams of fucoxanthin per day resulted in a significant weight loss compared with placebo after 16 weeks. The authors also reported increases in resting energy expenditure, decreases in body and liver fat content and improvements in the plasma lipid profile. Weight reductions were about 5kg (11 lbs) more in the supplemented group compared with the placebo group (the placebo group also lost a small amount of weight). However, caution must be exercised when interpreting these findings.


First of all, when results appear too good to be true, they often are. The dose used in this study was extremely small (2.4 milligrams), but the effects are rather large (5kg or 11 lbs more weight loss). As a first check one could check where the results are published. If it is a highly respected journal it may have gone through a more rigorous review process before it was published than a smaller unknown journal. Then one could look at the authors. Do they have a reputation? In this case, the journal was a respected journal. The authors did not seem to have an extensive publication record. In fact this seems to be their first publication in a major journal. When investigating this a little closer, at least one of the authors was working for the company that holds the patents for the commercial product that was used in the study. This does not mean that there is anything wrong with the data, but I would certainly like to see other studies independent of the patent holder or manufacturer that confirm these findings. At present such studies do not exist and thus we are stuck with too little evidence to draw any firm conclusions.


If a product claims that clinical studies have shown that a supplement promotes weight loss, reduce body fat and trim waist and hip circumferences, it would be good to see the details of such clinical studies. Before a supplement is recommended it should be supported by solid evidence. I have not even touched on the safety aspects as these are also relatively unexplored.

I hope this example shows how important it is to not simply believe the claims but investigate the underlying evidence a little more!



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