Updated May 22, 2019.
Published Jul 28, 2018.

Thermosyn, manufactured by The Skinny Caffe, is a weight loss supplement that improves the rate at which body fat is burnt, as well as providing a huge increase in energy levels. Some of the ingredients in Thermosyn have clinical support to suggest that they could aid weight loss, such as glucomannan, but the ingredient quantities are way too small to be effective. Furthermore, there is no money-back guarantee, and there is very little information available about the manufacturer.


  • Some ingredients have clinical support
  • Individual ingredients listed
  • Caffeine can give an energy boost


  • No money-back guarantee
  • Active ingredients present in very low quantities
  • Caffeine-related side effects
Thermosyn Weight Loss Capsules

Thermosyn Weight Loss Capsules Old Packaging

The Skinny Caffe products are recommended for those looking to lose weight, fast, and naturally. In particular, Thermosyn is a weight loss supplement that improves the rate at which body fat is burnt, as well as providing a huge increase in energy levels.

We will be taking an in-depth look at Thermosyn, to see if it really could help you to lose weight and to decide if it is safe to take.

Please note that although the packaging design has changed from the version to the right, the ingredients and quantities remain the same.

Thermosyn Overview

What you need to know about Thermosyn

Thermosyn Weight Loss Capsules are supposed to dramatically improve the rate at which body fat is burnt as well as providing a big increase in energy levels, using a combination of the strongest, most effective weight loss and energy ingredients available.

Thermosyn is manufactured by The Skinny Caffe, a health and well-being company based in the UK, who aim to promote an active, healthy, and balanced lifestyle to men and women globally. They also make weight loss coffees and teas. It is very hard to find any information out about the company, and it is only possible to contact them via a contact form on their website. It was only with some digging (and downloading their returns form) that we found out that they are supposedly based in Lancashire.

What are the side effects of Thermosyn?

There are many ingredients found in Thermosyn that could cause a range of side effects.

Glucomannan works by absorbing water in the stomach, making it really important to drink plenty of water when taking the product otherwise you could experience constipation and stomach cramps. As glucomannan is a fibre, it is likely that its use will increase the rate of bowel movements. Diarrhoea may also occur. Glucomannan also affects blood sugar levels. Diabetics should consult their doctor before taking any glucomannan-based product. Having said this, the amount of glucomannan found here is very small compared to the amounts used in clinical trials.

Acetyl L-Carnitine can cause side effects such as nausea, vomiting, stomach upset, heartburn, diarrhoea, and seizures. It can also cause the urine, breath, and sweat to have a “fishy” odour.

Caffeine is present in this supplement as a separate ingredient, but it is also found naturally in green coffee bean. Significant quantities of Caffeine can cause insomnia, nervousness and restlessness, stomach upset, nausea and vomiting, increased heart and breathing rate, and other side effects. Consuming large amounts of coffee might also cause headache, anxiety, agitation, ringing in the ears, and an irregular heartbeat.

Capsicum can cause increased sweating, stomach irritation, flushed skin, and a runny nose.

Chromium Picolinate can lower blood sugars levels, and as such should not be used by diabetics without first consulting their doctor. Low blood sugar levels can lead to light-headedness, dizziness, and even fainting.

How much does Thermosyn cost?

Thermosyn is expensive. It costs £25.00 for one pack for a 15-day programme, or £44.99 for two packs (30-day supply).

They do appear to offer regular discounts with pop-ups, as well as mention in the reviews of being able to purchase the product for £5.99!

The Skinny Caffe offers free shipping on orders over £15.00.

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Thermosyn Key Features

Thermosyn is a weight loss supplement that is available both on the official website, as well as on Amazon at a much lower price. The product information claims it helps to burn fat more quickly, as well as provide a huge increase in energy. It also contains Glucomannan which can help to suppress the appetite, however the levels present here in a daily serving are really low. Each capsule of Thermosyn contains only 100 mg of Glucomannan, making this ingredient incredibly unlikely to have the desired effects.

Thermosyn Key Points

  • Contains 30 capsules per packet (15-day supply)
  • Manufactured in the UK
  • Contains caffeine from two different sources

Caffeine will increase energy levels and potentially cause a slight increase to the body’s metabolic rate for a few hours after consumption, but you could get the same effects from just drinking coffee at a much cheaper price!

Green coffee bean is another source of caffeine, but has no current strong clinical research linking it with significant weight loss. The main supporting study was found to be fraudulent and was retracted in 2014.

How to Take Thermosyn

  • To support weight loss: Take 1 capsule 2 times a day 4 to 6 hours apart
  • For Energy/Pre Workout: Take 2 capsules 45 minutes prior to workout

Raspberry fruit extract has never been tested in humans for weight loss purposes, but animal and test tube studies suggest that it could aid weight loss. L-Tyrosine may reduce fatigue, but it does not appear to have any effect on weight loss and the levels present here are quite low.

Thermosyn Concerns

  • No money-back guarantee
  • Very little information about the company available
  • It is expensive with very low quantities of ingredients

Theoretically, some of the ingredients could aid weight loss, if they were used in the correct quantities. However, it appears that most of the active and clinically proven ingredients are present in insufficient quantities to effectively aid significant weight loss consistently.

What does Thermosyn claim to do?

Thermosyn is claimed to provide weight loss by increasing the rate at which the body burns fat as well as suppressing the appetite, and also give increased energy.

Does Thermosyn work?

We think it is very unlikely to meet this claims as the majority of these ingredients are highly under-dosed.

A consumer could receive a burst of energy after taking this supplement due to the high levels of caffeine included, however the effects of this will be temporary and potentially come with side effects.

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Thermosyn Ingredients

  • Glucomannan 100mg: Natural dietary fibre made from the root of the Konjac root. It is becoming well known as a weight loss aid. It is a bulk-forming laxative, which means that it causes the bowels to open because of the fibre content unlike laxatives such as Senna that irritate the gut lining. Effective serving size is 3000mg a day. Source
  • Caffeine 83.34mg: A stimulant, supposed to work by activating certain pathways involved in metabolism. Unfortunately, there is not enough evidence to suggest that regular intake of caffeine can produce all these benefits.
  • Acetyl-L-Carnitine 50mg: A compound of the amino acid L Carnitine and is often taken for its brain-boosting capabilities. It helps the body produce energy and clinical testing has found that it can improve memory function and depression, and increase blood flow in the brain. Source
  • L-Tyrosine 50mg: An amino acid that is a building block of protein. Large doses may be useful for increasing alertness, especially in people who are sleep deprived. Source
  • Raspberry Fruit Extract 500mg: Natural leaf extract used for a wide range of ailments. Its principle use seems to be around menstruation and easing labour pains. Raspberry leaf may have medical benefits but it lacks clinical evidence at this time. Source
  • Green Coffee Bean 1000mg: Contains caffeine. Whilst it was thought that this ingredient was a significant aid in weight loss, the relevant research has been discredited as it was fraudulent. Currently, there is no evidence that it aids with weight loss more than any other source of caffeine. Source
  • African Mango 250mg: Used for centuries for its medicinal properties. It is mainly because of its weight management properties this fruit has been under research for decades now. The actual weight management substance, however, lies in the seeds of this fruit which is extracted to create the supplement. Whilst many of the studies of African Mango have been funded by supplement manufacturers (which makes them automatically biased), there are promising preliminary results that suggest IGOB131, a substance extracted from African Mango, suppresses the appetite and leads to weight loss. Source
  • Capsicum 100mg: Thought to play a role in weight loss. Some studies suggest it could suppress the appetite mildly, whilst others suggest that the heat causes a thermogenic reaction in the body, burning more calories for a period of time. However, there are also studies that show capsicum extract has little or no effect upon weight loss attempts.
  • Bladderwrack Extract 175mg: This sea vegetable is a concentrated source of minerals, including iodine, potassium, magnesium, calcium, and iron. Iodine assists in the production of thyroid hormones, which are necessary for maintaining a healthy metabolism in all cells of the body. If a person has no thyroid problems and does not have an iodine deficiency, this ingredient will do little to boost weight loss attempts. Source
  • Standardised to contain 1% Iodine 50mcg: Helps activate an inactive thyroid gland and protects it from possible radioactive damages. Boosts metabolism and leads to long-term weight loss. Leads to improved breast, ovarian, neurological, and organ health.
  • Chromium as Picolinate 66.67mcg: Used primarily to lower fasting blood sugar levels and to lower insulin levels in people who have type 2 diabetes. In terms of its potential effect upon weight loss, it is possible that taking chromium picolinate by mouth for 2 to 3 months might produce a small weight loss of about 1.1 kg. Obviously, this is an incredibly small amount, and studies are still inconclusive. It also helps to reduce insulin resistance. Source
  • Other ingredients: Colourants Titanium Dioxide E171 Yellow Iron Oxide E172, Red Iron Oxide E172, Azorubine E122 (Gelatine Capsule Microcrystalline Cellulose) Magnesium Stearate.

Thermosyn Side Effects

There are many side effects associated with the ingredients in Thermosyn.

Glucomannan can cause side effects if enough water is not consumed alongside it. These include constipation and stomach cramps.

Acetyl L-Carnitine can cause:

  • Nausea
  • Vomiting
  • Stomach upset
  • Heartburn
  • Diarrhoea
  • Seizures
  • Can give a “fishy” odour to urine, breath, and sweat

Caffeine can cause:

  • Insomnia
  • Nervousness and restlessness
  • Stomach upset
  • Nausea and vomiting
  • Increased heart and breathing rate
  • Headache
  • Ringing in the ears
  • Irregular heartbeats

Capsicum can cause:

  • Increased sweating
  • Stomach irritation
  • Flushed skin
  • Runny nose

Chromium Picolinate can lower blood sugar levels which can lead to:

  • Light-headedness
  • Dizziness
  • Fainting
Caution: Do not take if you have a known medical condition. Always consult a medical professional if unsure about suitability. Discontinue immediately if sleeplessness or nausea occur.

Thermosyn Customer Feedback

We couldn’t find any independent reviews for Thermosyn. There are a number of reviews on the official website but it is hard to know whether these are genuine, especially as they are all positive.

An example includes:

I used a pack of Thermosyn for 15 days and lost 6lbs. I am looking forward to using these more and seeing how much weight I can lose.

Thermosyn Money-Back Guarantee

No, Thermosyn does not offer a money-back guarantee.

Where To Buy Thermosyn

You can buy Thermosyn from the official website for £25.00 for a 15-day supply, or £44.99 for a 30-day supply.

Watchdog Verdict

Some of the ingredients in Thermosyn have clinical support to suggest that they could aid weight loss, such as glucomannan, but the ingredient quantities are way too small to be effective. Other ingredients have not been studied enough to know if they would actually have positive benefits. Raspberry fruit extract has never been studied in humans, but studies in animals and test tubes suggest that it could theoretically aid weight loss.

Although each capsule contains slightly less caffeine than a cup of coffee, there is still a high dose taken with the green coffee bean in Thermosyn. It could, therefore, cause side effects, especially if taken on an empty stomach, late at night, or if the consumer is still drinking caffeinated drinks whilst taking this supplement.

It is an expensive product, although there are often offers on such as multi-buy or student discount to get it at a discount at a lower price. However, there is no money-back guarantee on the product, which does concern us, particularly as there is very little information available about the manufacturer.

Due to all of these concerns, we do not recommend Thermosyn to our readers.

How does Thermosyn compare to Phentaslim?

Criteria Thermosyn Comparison Phentaslim comparison
Clinically Proven Ingredients
Side Effect Free
Positive Customer Reviews
24/7 Support
Money-back Guarantee

Disclaimer: Our reviews and investigations are based on extensive research from the information publicly available to us and consumers at the time of first publishing the post. Information is based on our personal opinion and whilst we endeavour to ensure information is up-to-date, manufacturers do from time to time change their products and future research may disagree with our findings. If you feel any of the information is inaccurate, please contact us and we will review the information provided.

Have Your Say

1 comment on 'Thermosyn'

  1. MISLEADING AND FRAUDULENT- My advice is to stay well clear of this company and it’s endorsers. It’s a very clever ploy from the company to get big named stars to promote this product which NONE of whom mention that the reason for the free packet is that it leads in to a six month contract you can’t get out of. Very clever wording after you place your initial order which states you can’t cancel as it’s a discounted product.
    I saw that many stars were spamming their pages endorsing this product so I decided to give it a go. Yes I am an idiot for trying a quick fix diet but having mental health problems and eating disorders I am sucked into these things easily, just like thousands of women who are desperate to loose a few pounds. Most of the reviews were ok but since I have been trying to contact them I have realised hundreds of comments are being removed if they are anything less than pro Skinny caffe.

    It was originally meant to be a free 14 day supply if you click on the link that the celebrity’s post it doesn’t work. It’s a 14 day supply one off payment! It is not stated else where this is a subscription. As you can see the company fully admit the subscription email is sent after you ‘think’ you’ve made a one off purchase. How is this helpful to tell you AFTER?

    I like many others have more than likely been dubbed into thinking I was getting a great deal but now trapped into a subscription service without my knowledge.

    If the product is as amazing as it claims to be you do not need to trap people in to a subscription. I for one would have been more inclined to try the product and if it worked well to repeat my order monthly of my own accord. By taking away my choice to do this, like many others, people panic. They instantly want to return their product before they even try it.

    I sent an email stating I did not want a subscription service and I was inform by Gemma That I have no choice and I can not cancel this and she sent me a link for the terms and conditions! Again, instantly peoples back go up and they feel trapped. You don’t need to bully people in to a contract if the product is as good as it says it is.

    As I read the terms and conditions I can infact cancel within 14 days! I have contacted various third party websites, banks and trading standards all which say I am in my rights to cancel this subscription. Why do you need to initially tell people they are tied into something? So the less clued up are in fact now terrified to dig further, they give up and you get an unwanted subscriber but hey you get you money right?? That’s all that matters.

    Gemma stated that I have agreed to the terms and conditions which I have not. The subscription information was sent after my initial order which I was led to believe to be a one off. I decided to do another test order without putting my cards details in again and I also got some friends and family to do the same. It was then confirmed there is no where when purchasing this product does it state this is a subscription.

    Please stay clear of this company and Unfollow any of the celebs who endorse these products/companies especially to young impressionable people. Unless they change their policies and let you make up your own mind if the product works without tying you down into a misleading contract. Then maybe people wouldn’t be so adamant about this company scamming people.

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