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Best Thermogenic Fat Burners – UK Reviews

Do you find it more difficult to burn fat or gain muscle? Everybody has strengths and weaknesses. If you’re somebody who struggles to stay lean or lose weight, you might want to consider adding a thermogenic fat burner to your supplement stack.

In this article, we’ll start by explaining how you can best use fat burners to maximise your workout results. We’ll also look at the research behind some of the most common ingredients to see which are active ingredients and which are filler.

Pot of thermogenic fat burner capsules

After that, we’ll finish the article by breaking down some of the more popular fat burners to help you find the one that fit your goals. Let’s get to it.

Editor's Choice
Grenade Thermo Detonator

Grenade Thermo Detonator

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Grenade Black Ops

Grenade Black Ops

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Adrian James Nutrition Thermoblaze

Adrian James Nutrition Thermoblaze

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Best Value
Freak Athletics F5

Freak Athletics F5

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Freak Athletics Thermo 1.0 Xtreme Thermogenic

Freak Athletics Thermo 1.0 Xtreme Thermogenic

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Somatox Extreme Fat Burner Max

Somatox Extreme Fat Burner Max

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Note: There’s a lot more information below but clicking the above links will take you to current prices, further information and customer reviews on Amazon or Best Gym Equipment.

A Detailed Look at the Best Fat Burners

Each fat burner relies on a different formula to maximise your fat loss. We’ve compiled a list of the most common supplements on the market (all are available in the UK). We’ve also broken down the specs of each to help you find one that works for you.

Grenade Thermo Detonator provides you with six ingredients to boost your metabolism. This product is suitable for both men and women and is marketed toward athletes, military members, and fitness enthusiasts.

Each grenade-shaped container contains 50 servings designed to be taken before a cardio or HIIT workout. At least four of the ingredients in Thermo Detonator are research-backed.

No matter whether you’re a weekend warrior or a world class athlete, Thermo Detonator can help you cut body fat.


Overall, Grenade put together a solid product with Thermo Detonator. In the buying guide, we listed four ingredients that have compelling evidence to support them as fat burners. This supplement contains all four.

The biggest downside is it contains bitter orange, which may cause health problems in rare cases.

Things We Like
  • Contains a good blend of research-backed ingredients
  • Clearly labels the doses of each ingredient
  • Good price per serving
Things we don’t like
  • Contains bitter orange

This is the second fat burner by Grenade on this list. Black Ops has a shorter duration of effect than their original Thermo Detonator. It’s designed to be taken before your workout to increase your fat oxidation.

This fat burner contains a long list of ingredients designed to support your body’s energy production. Unlike Thermo Detonator, it doesn’t include bitter orange, so a better choice for those that want to avoid it.

Black Ops contains 295 mg of caffeine per dose, so you’re sure to feel a boost in your energy no matter how lazy you’re feeling.


Black Ops is supposed to provide you with a shorter boost of energy than Grenade’s original Thermo Detonator. It contains a very high amount of caffeine. If you’re particularly sensitive, you may want to go with a different supplement.

Things We Like
  • Good blend of ingredients
  • Relatively cheap
  • Avoids bitter orange


Things we don’t like
  • Not suitable for people with low caffeine tolerance
  • Missing green coffee bean extract

Thermoblaze has thermogenic properties and is made from a blend of herbal supplements and vitamins. It’s also the first supplement that we’ve looked at that’s manufactured in a GMP approved facility, meaning this product undergoes rigorous quality checks.

Thermoblaze also contains all four ingredients we found to be most effective at speeding up your metabolism. If you’re looking for a good fat burner that avoids potentially dangerous ingredients and unsafe manufacturing processes, this fat burner makes a great choice.


A good choice if you’re sensitive when taking too much caffeine. It only contains 166mg of caffeine per serving whereas some fat burners contain more than 250mg. Even though it contains all four of the top fat-burning ingredients, you can still get it for a great price.

GMP approved, so you can take it without worrying what hidden ingredients might be in it.

Things We Like
  • Made in a UK GMP facility
  • Contains green tea extract
  • Includes cayenne powder (capsaicin)
  • Money-back guarantee
Things we don’t like
  • Only 30 servings per container

F5 contains three of the ingredients we found to be most effective at helping you burn fat: green tea extract, cayenne powder (capsaicin), and caffeine.

This supplement only contains 125 mg of caffeine per serving (slightly more than the average coffee). However, the company recommends that you take two servings per day.

This supplement provides you with the caffeine jolt of your morning coffee while also providing you with the benefits of green tea and cayenne.


This fat burner contains a relatively low dose of caffeine compared to other brands. However, it’s recommended that you take two servings per day, one in the morning and one before your workout. F5 makes a good choice if you’re looking for something that will stimulate your metabolism without making you wired.

Things We Like
  • Made in the UK
  • Contains green tea extract
  • Doesn’t contain bitter orange
Things we don’t like
  • Would be good if it also contained green coffee bean extract

Thermo 1.0 Extreme Fat burner contains a short list of ingredients compared to the other fat burners we’ve looked at. The two key ingredients in this product are caffeine and green tea extract. It also contains bitter orange, which is one of the ingredients that may have negative side effects.

Most fat burners contain a long list of ingredients as filler. At least three out of four of the ingredients in this product have research to back them (including bitter orange). A shorter ingredient list means you’re less likely to have a negative reaction from one of the ingredients.

If you’re looking for a simple and cheap fat burner, you may want to consider Xtreme.


A lot of products include a long list of ingredients that don’t have research to back them. However, this product sticks to just four solid ingredients. If you’re looking for something cheap and easy, it’s hard to go wrong with this product.

Things We Like
  • Well priced
  • Contains 500 mg of green tea extract
  • 45 servings per container
Things we don’t like
  • Contains bitter orange
  • Missing green coffee bean extract
  • Missing capsaicin

Extreme Fat Burner Max is another supplement made in a UK GMP approved facility. It contains five ingredients to speed up the rate your body burns fat.

This supplement contains one of the highest caffeine content of any supplement on the market at 300 mg. It also contains a high amount of bitter orange, which is one of the ingredients that has been linked to potentially harmful side-effects.

However, it’s worth noting that in at least one case linking bitter orange to stroke, the supplement was mislabelled and actually included a more dangerous stimulant Ephedra. Because this product is made in a GMP facility, it’s checked for potential mislabelling.

This fat burner can help you feel the metabolism boosting effects of caffeine even if you consume a large amount of caffeine daily.


This product contains one of the highest doses of caffeine of any of the supplements we’ve looked at. If you have a strong caffeine tolerance this may be a good option for you since it contains 300 mg per dose.

Things We Like
  • Contains green tea extract
  • Extremely high in caffeine
  • GMP certified


Things we don’t like
  • Contains bitter orange peel
  • Missing capsaicin
  • Missing green coffee extract

What is a Thermogenic Fat Burner?

Thermogenic fat burning supplements contain ingredients designed to boost your metabolism and therefore lose fat. They’re usually made from a blend of ingredients extracted from various plants.

Almost every fat burner contains caffeine. Many also include extracts from green tea, cayenne pepper, green coffee beans, and bitter orange.

How Do Fat Burner Supplements Work?

Each fat burner tackles fat loss differently depending on their ingredient mix.

Many fat burner supplements directly stimulate your metabolism. Your metabolism is set by several factors including your age, the amount of muscle mass you have, and your genetics. When your metabolism rises, your body breaks down fat cells quicker for energy.

There are a few ways this stimulation can occur. Caffeine signals for the release of the hormone adrenaline (epinephrine in the USA). Adrenaline signals to your body to break down fat quicker.

Other ingredients like bitter orange and green tea extract increase the amount of time this hormone circulates through your veins before breaking down.

Some supplements suppress your appetite. The hardest part when cutting weight is usually ignoring hunger pangs. Fat burners with appetite suppressing effects can help you navigate these food cravings.

It’s important to note that you should your expectations somewhat. There’s no miracle supplement that can transform your body for you. If you don’t plan on training hard with a regular exercise routine and eating a clean and balanced diet, you’ll likely be disappointed with your results.

However, if you use a fat burner to complement your already good habits, it might help you achieve a new level of leanness.

Typical Key Ingredients

We’ve assembled a list of some of the most common ingredients you can expect to find. We’ve broken them into three categories: ingredients with strong evidence to back them as fat burners, ingredients with weak evidence, and potentially dangerous ingredients.

Ingredients with Strong Evidence

These Ingredients have strong evidence to back them as having fat burning potential.


Caffeine is one of the top ingredients used in fat burners. The metabolism-boosting effects of it are well-documented. As we’ve mentioned, caffeine works by stimulating the amount of noradrenaline (referred to as norepinephrine in the USA). circulating through your blood.

Caffeine also inhibits the chemical adenosine in your brain, which makes you feel more awake. This effect may indirectly lead to fat loss by motivating you to move more.

Green Tea Extract

It’s thought that the antioxidant EGCG in green tea inhibits the rate that your body breaks down the hormone noradrenaline. As we’ve already said, epinephrine increases the breakdown of fat cells.

Green tea extract may be particularly beneficial if you take it before your workout. There’s research that shows taking green tea extract before a workout may lead to increased fat breakdown and improved insulin sensitivity.

Green Coffee Bean Extract

Green coffee bean extract comes from unroasted coffee beans, and it contains a compound called chlorogenic acid. The process of roasting coffee beans breaks down this healthy chemical.

One review of studies found that green coffee bean extract has the potential to moderately increase your body’s fat metabolism. More research needs to be done, but early results are promising.


Capsaicin is the chemical found in spicy peppers that gives them their kick. If you’re a lover of spicy food, you’re in luck. Research shows that this chemical dulls your appetite and increases the rate your body breaks down fat cells.

You may also see cayenne listed in the ingredient list of some supplements for its high concentration of capsaicin.

Ingredients with Weak Evidence

These ingredients may help you burn body fat, but it’s not clear how strong of an effect they have. Right now, there’s either little research or no research to back them.


L-carnitine is a non-essential amino acid that your liver and kidneys produce and store in your muscles. This amino acid mobilises fatty acids to your mitochondria to be used for energy.

It’s thought that taking L-carnitine before a workout may increase the rate that your body oxidises fat. Right now, it’s not clear how much of an effect it has on humans.


Many fat burners contain B vitamins and vitamin C. These vitamins play an important role in your overall health, but they’re unlikely to help with burning fat.

African Mango Extract

At this time, there’s no compelling evidence that mango extract does promote weight loss. Many of the studies that have found potential fat-burning effects were sponsored by supplement companies.


Yohimbe is made from the bark of the Yohimbe tree. It may help with fat loss by inhibiting alpha-2 adrenergic receptors. However, research is mixed at the moment.

Raspberry Fruit Ketones

Dr. Oz promoted raspberry ketones for weight loss on his television show. Some people believe these ketones can increase the efficiency that your body burns fat. However, right now most studies show they have little or no effect on fat-burning.

Potentially Dangerous Ingredients

These ingredients have potentially harmful side effects.

Bitter Orange

Bitter orange is one of the more controversial ingredients but it is quite common. A review of studies found that participants had modest amounts of weight loss after taking bitter orange for 6 to 12 weeks.

Bitter orange contains a substance called synephrine. This substance is structurally similar to the hormone epinephrine in your body. There have been a few case reports of stroke and angina in people taking bitter orange supplements.

More long-term research needs to be done to examine bitter orange’s effects on your body. If you want to avoid the risk altogether, you may want to stick with a supplement that doesn’t contain this ingredient.

Garcinia Cambogia

This tropical fruit contains the ingredient hydroxycitric acid. It’s a well-researched ingredient that research consistently shows can cause a small amount of weight loss. However, there have also been a few cases of it causing liver damage.

What Are the Benefits of Thermogenics?

As we already mentioned, no supplement can completely transform your body unless you’re willing to work for it. If you’re training hard and eating clean, adding a fat burner to your stack may optimise your results.

You’re not going to lose five kg per week on a thermogenic supplement. It’s difficult for most people to lose more than 0.5 kg per week of body fat. If you have a realistic plan of the body you want to achieve and the timeframe you want to achieve it, a fat burner can support your goal.

Are There Any Side Effects?

Some fat burners may cause side effects. Each supplement contains a different mix of ingredients, so the potential side effects vary between brands.

It’s fairly safe to say that most fat burners contain caffeine. Some of caffeine’s common side effects include the following:

  • Rapid heartbeat
  • Heart palpations
  • Digestive problems
  • Anxiety
  • Insomnia
  • High blood pressure

Some other common side effects include the following:

  • Nausea
  • Headaches
  • Restlessness
  • Dizziness

It’s always a good idea to monitor how your body responds to a fat burner to see if it’s negatively affecting your body. If you notice any negative side effects, it’s a good idea to stop taking that product.

Are They Safe?

Most fat burners are relatively safe. However, if you’re particularly sensitive to caffeine, you might want to choose a fat burner with a lower dose of this ingredient. The average cup of coffee contains around 100 mg of caffeine and some fat burners contain 250 mg or more.

It’s also worth noting that it’s a good idea to cycle on and off of fat burners. Cycling will give your body a chance to reset from the high amounts of caffeine and other ingredients.

If you want to take the safest supplements, look for brands that have GMP approval. GMP stands for good manufacturing practice and means that the product has to undergo rigorous safety checks.

How Do You Get the Best Results from Fat Burners?

The best time to include fat burners in your supplement stack is during your cutting phase. You’ll likely want to cycle off when you’re not trying to lose excess body fat. If you take them during your bulking phase, you may end up slowing down your weight gain.

It’s also a good idea to consider what time of day you’ll be working out before taking them. Because they generally contain high amounts of caffeine, taking them in the evenings may affect your sleep quality.


Each fat burner has a slightly different formula. The ingredients that have the most research to back them in aiding fat loss are caffeine, green tea extract, capsaicin, and green coffee bean extract.

Grenade Black Ops is the one for those that like their fat burners to provide a kick. It contains 295mg of caffeine per serving and also provides you with the benefits of capsaicin and green tea extract.

If you’re looking for something lower in caffeine, you may want to consider Adrian James Nutrition’s Thermoblaze. It contains less caffeine than some but includes a great blend of herbal ingredients. It’s probably the one that will suit the most people.

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Jason Barnham

Jason started lifting weights back in 1990 which sparked his interest in Nutrition. He went back to college in 1993 then started at the University of Surrey in 1994, graduating in Nutrition and Dietetics in 1998.

Having worked in both the NHS and running his own dietetic clinic, he has now settled into the web publishing world.

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