Raspberry ketones for weight loss – get ready for a surprise

By Dagmar
In Discussion
Apr 21st, 2015

I am having enough of the spam e-mails coming to my mailbox about cheap raspberry ketones for weight loss. The raspberry ketones pills and capsules seem to be everywhere and the media are only supporting this business based on unfounded claims. What made me to write this article was this offer by Holland and Barrett when I bought some items online and this came up on my screen after I finished the purchase.


That was the last straw for me and I have decided to share with you the truth about 1. how all this hype is not sufficiently supported by the science and 2. what may have been behind this in the first place.

1. The lack of scientific evidence to support the claims

As I did not do a vigorous research on this topic before, I started with what other nutrition and health professionals have to say about this. Becky Hand, a registered dietitian, posted a spot on article on HuffPost in 2013: What they don’t want you to know about raspberry ketones. There she said that no human studies about the effect and safety were conducted by the time of writing that article and how the small print had to mention that FDA does not monitor the safety or effect of products like this, which are not medicines. There was an odd study on rats or on cultured cells, but that was it. No more research on raspberry ketones and definitely none with a proven effect on humans. However, that was two years ago. The weight loss supplementation has been a huge business for decades so I hoped there might have been more research done since then. Was it?

Promising results but not for humans (yet)

PubMed, one of the largest online database of life sciences and biomedical abstracts, shows nothing new when you type in key words: raspberry ketones weight. It offers four studies dated back to 2010 and before but two of them are not even related to the body weight at all. The two remaining studies were conducted on rats and mice, in both cases fed with high-fat diet despite the rodents are primarily starch eaters. These studies were exactly those listed in the dietitian’s article above.

When searching more broadly with the raspberry ketones keywords only, the PubMed showed overall 41 results, of which only two other looked interesting on the first sight. However, these also were not relevant to the obesity and weight loss. One study examined the effect of raspberry ketones on breast cancer cells in vitro and the remaining one studied the ketones effect on the non-alcoholic fatty liver disease – in rodents again.

This just confirms that up to date no peer reviewed studies about the effect of raspberry ketones on weight loss have been conducted on humans and published. The fact is that even if these ketones had the effect, we do not know about the safe or effective dose and the short or long term consequences on human metabolism and health. And I have already mentioned that rodents are not naturally high fat eaters. They are starch eaters; their metabolism is different from ours and the study on rodents therefore cannot be used to imply the effect of raspberry ketones on humans.

Manipulation with the customers’ minds

After all, my enthusiastic search was rewarded with information that there was made at least one study on humans. What did they find?

“The one human study to investigate the effects of raspberry ketone found a fat loss of 7.8% relative to the 2.8% in placebo, and weight loss of 2% relative to 0.5% in placebo…”

However, the source admit that this study was heavily confounded. On top of that, there was no statistical significance of the results mentioned, nor the number of participants, their age, body weight, and other important information for the critical evaluation of the study and therefore its quality. No wonder it did not appear in PubMed. The basic rule is: what was not listed in the peer reviewed literature should be taken with a pinch of salt. Anybody can report anything and design the study they want for the results they desire but I will not take it seriously. Nobody should. Regardless, the lack of solid evidence did not stop the manufacturer and the marketer to promote their product as a success:



That caffeine, capsaicin, ginger and other compounds were those confounders. We do not know which compound was more effective but this was aiming to sell the product containing the whole cocktail of these substances, not just the raspberry ketones. The ketones were only a vehicle for the product to the customer’s hands (and for their money flowing to the company) because the raspberry ketones are currently such a hot topic.

On the same website in a separate page of RASPBERRY KETONE PLUS REVIEW you could read:

Naturally, these effects will occur only if the raspberry ketone supplement actually contains pure raspberry ketones and in the right concentration, which is 200 mg.”

Well, not only this amount has no scientific background, they cannot even get the terminology right. The concentration means the amount of dissolved substance per unit of volume, not the total weight of the substance. There was more nonsense published in their ‘review’ but I do not need to dig into it too much as it is obvious the whole review is just a marketing propaganda without any evidence to support its claims.

From my curiosity, I contacted the Bauer company on their original website twice with a query about having a look into more detail of the study they referred to. First time my query was supposed to be forwarded to the relevant team and dealt with. Because it did not happen within a couple of days, I tried again. Then I was advised to send an e-mail directly to the team. A week has passed and nothing has happened. It may take time or they will not reply at all. I predict the latter. Regardless, the study does not seem to be up to the standard of the proper scientific research and it should be considered as not valid. This lack of validity refers to the effect of the raspberry ketones alone, especially when the company has already admitted the confounding. We simply know little or nothing about the raspberry ketones for weight loss in humans. Yet the market is full of this product, providing different doses to customers but nobody knows for sure what the effective dose is.

Possibly ineffective doses are on the market

Now, let’s look more closely on the amounts needed to be consumed by the customers (theoretically, of course). If we used the amounts which were found effective on the rodents, a human subject would have to consume a mammoth dose of raspberry ketones, equivalent of 1.1 up to 5 grams for 200 lb / 90 kg heavy person (source). Quite a difference from the mean 200 mg or even the ‘extra high strength‘ coming from 500 mg product sold by Holland & Barrett you will see below. For the maximum result you would have to consume 10 Holland & Barretts extra high strength capsules per day, or ‘only’ two for the lowest effective dose confirmed on the rodents. Do your math and see how many days would the 90 capsules bottle last for those £29.99 (April 2015) if you aimed to achieve the top effect (still not confirmed for humans, bear in mind). Would you be ready to fork out  £20 to £100 each month for the product the effect of which has not been tested on humans?  No wonder they want to get rid of those 100 mg pills they were promoting to me previously. They already have them reduced to half price.

Are raspberry ketones for weight loss banned in the UK?

Holland & Barretts raspberry ketonesIt was quite a surprise for me to read that these supplements are sold illegally in the UK. Two independent sources (one and two) introduced me to this information that under the EU legislation and according to the statement of the Food Standards Agency (FSA) in the UK, the raspberry ketones are classified as unauthorized novel foods. I have checked the FSA documentation and they clearly state that the product used as a specific flavoring or  the “extracts prepared using water or 20% ethanol (1:4 ethanol:water)” are an exception from the novel foods category, therefore these are legally sold in the UK. I sent a brief e-mail to Holland & Barrett asking for more information. They replied the next day (at the weekend, thumb up for the great customer services) and they confirmed that “all Holland and Barrett raspberry ketones satisfy this requirement“. Therefore at least their product is legally sold in the UK.

In addition to this, as a reply to their first answer I asked the Holland & Barrett another question: Is there any research supporting the dose and effect of these ketones on the weight loss in humans? They are selling the product so I hoped they have some sound background for it. The truth? Nope, they do not. Their answer came after four days and it contained a honest information that no human studies were conducted on the effective dose of raspberry ketones. They also wrote:

“…anecdotal reports suggest that 1000 mg per day ‘may be’ the optimal dose. For those new to supplementation with raspberry ketones it is best to start on a lower dose product (e.g. the 100 mg product we sell) and build up gradually to allow the customer to gauge their own personal tolerance to the effects of the product.

Again, those 100 mg capsules. Although there is no evidence for the effective dose except of some anecdotal reports (confounded? placebo? whose reports?), they try to convince me with the lower then lowest proven dose on rodents (it was 1100 mg as equivalent to humans). And, by the way, why not helping them to clear the shelves full of those 100 mg capsules (possibly close to their expiry date) which might have no effect at all, to build a tolerance to their effect…

I continued to pester them with another question. Again, it took them a few days but they did reply. I specifically asked about what they meant by the tolerance. This term can be viewed from different contexts:

  • a) a person had an initial adverse reaction but with the continuation of using the supplement this reaction disappears;
  • b) as with drug addiction, the person will become unresponsive (developing tolerance) to the substance and/or dose and a higher dose will be needed to achieve the same result as before.

Their response was:

“What is meant by that term is how an individual may react to a certain product. For example, this could cause some people to feel light headed due to the effect it has on blood pressure etc.”

Here we go… the side effects. There are abundant reports about the side effects after using raspberry ketones among the customers on the web. Those are the anecdotal reports of people who simply tried the product and noticed something happening to them, sharing it with others. This could have or could have not had anything to do with the actual product, exactly the same as the weight loss effect reported by other anecdotal reports. We know nothing about those people, their health condition, their diet, or a possible contraindications if they took some medicine or some other supplement. We know nothing. Would you risk it? I would not. I rather enjoy a handful of fresh raspberries with all their natural and complex goodness.

The verdict:

  1. There was found no proven effect and neither effective nor toxic doses have been established for humans, because
  2. There was made no legitimate research on humans.

The company/companies are simply satisfying the market demand and provide the substance to generate profit while meeting the legal criteria (at least some of them). That is all. And, by selling these low doses of active compound, they are probably hitting two nails at once: if it is ineffective it might also be safe to sell it to the naive folks. I have a colleague, who is struggling with her weight and tried some of these raspberry ketones from Holland & Barrett. She said that she noticed no effect at all. Just saying.

2. Ketogenic diet is not the same as supplying additional ketones to the normal diet

I must admit that I do not have information about how this concept of raspberry ketones as a supplement for weight loss came to be. What I suspect is that the scientific community agrees on the health benefits of ketogenic diet in some people. For example, people suffering epilepsy have experienced fewer seizures when being on the ketogenic diet. Or Atkins diet is notoriously known for producing ketogenic state -> promoting weight loss and improvement in other metabolic markers such as blood ‘cholesterol’ or better glucose control in diabetics. What that actually means?

Ketogenic state occurs when fats are burned as the primary fuel instead of glucose which has been depleted in the body and not much is provided in the low-carb/Atkins/ketogenic diet. It is quite popular today and I understand why. To cut a long story short, when you exclude carbohydrate from your diet (bread, pasta, potatoes, rice, sugar), the glucose stores in the body are soon depleted. Because the entire body likes burning glucose as a primary and easy and quick source of energy, the body has to switch to altered metabolism and burn fats and proteins as the main source of energy instead. Brain cannot use fats or proteins as a source of energy though. It is, however, able to run on ketone bodies, which are a by-product of fat break down.

The lack of carbohydrates in the system also keeps insulin levels down. That enables the fat cells to release fatty acids for metabolism and that is why the Atkins diet works so well for weight loss. When the insulin rises after carbohydrate consumption, it enables the cells utilizing glucose. However, at the same time the insulin helps clearing available lipids from blood into the fat cells. So if you have eaten sweet and greasy meal, you will primarily burn the sugar and the fat will go straight to the fat stores. Simply said, when there are spikes in insulin, fat loss is diminished.

Now, where the raspberry ketones come into this? The whole concept of raspberry ketones is completely different from the ketogenic state we induce upon ourselves when we are excluding carbohydrates from our diet. The ketogenic state is like a starving mode – you burn your fat stores instead of filling them or maintaining them. In contrast, you can feed yourself with raspberry ketones even when you are overeating, drinking sugary drinks, eating sweets, etc, i.e. storing fat at the same time. People are usually not in a ketogenic state when consuming raspberry ketones. And that is the point. Customers are being sold expensive supplement without having any proven safety and effect on humans as such. It is only when they attempt to lose weight and go on some diet, often coupled with exercise, where the raspberry ketones have some potential as an additional boost. But the dose has not been tested so you may well be paying a lot of money for placebo.

Raspberry ketones from GMO

Several studies have been published in the past years about how raspberry ketones can be synthesized by genetically modified bacteria. The scientists can transfer a raspberry gene into a bacterium so it can produce compounds identical to the expensive raspberry ketones obtained from the fruits but at a significantly lower cost. Have the market caught up with that already? Based on the claims that the raspberry ketones are flying off the shelves I think that it would be difficult to satisfy the demand the old fashioned way – naturally by growing and processing huge amounts of raspberries. Are the customers being ripped off? How would it affect the novel food status of such products without a proper research available? Or was it only aimed at the perfumery industry and that specific flavoring compound mentioned earlier? So many questions are calling for the answers.

For now I will enjoy a bowl of berries, which contain a whole cocktail of beneficial compounds for my health, not just some ketones. Eating such a satisfying treat will also curb my appetite for unhealthy and caloric food, preventing a weight gain in the first place.

About "" Has 48 Posts

Graduated at London Metropolitan University: BSc (Hons) Human Nutrition in 2014. Working as a research assistant at the MRC, The University of Cambridge.

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