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A pouch of The Define Booster - acetyl l-carnitine supplement by Innermost
A pouch of The Define Booster - acetyl l-carnitine supplement by Innermost
A pouch of The Define Booster - acetyl l-carnitine supplement by Innermost
Ambar Driscoll smiling and looking confident for Innermost
Pouches of The Define Booster - acetyl l-carnitine supplement by Innermost
The Define Booster white powder - acetyl l-carnitine supplement by Innermost

The Define Booster

Definition done properly.

To decrease body-fat you need the right nutrients. That’s where this product comes in. The most popular non-stimulant fat-loss supplement in the world. It works by ensuring your body is metabolising fat efficiently. Live life in High Definition.

The Define Booster

Unflavoured with a slightly bitter taste | 200g

£29.95 £29.95

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Product Highlights

Active Ingredients

For every serving of The Define Booster: Acetyl L-Carnitine (2g).

Scroll down to learn about these ingredients and how they benefit you.

This product is vegan, cruelty free, gluten free, lactose free, soy free, halal, suitable for kosher diets, non-GMO, and free from all 14 major allergens. Furthermore, the product contains no artificial fillers, bulking agents or colours, and our packaging is 100% recyclable.

How And When To Use

To be taken during the day, once a day.

Directions: Mix 2g (1 flat teaspoon) with around 200ml water or juice in your Innermost shaker bottle, or simply add 2g to your pre or post-workout protein shake. Unflavoured acetyl l-carnitine does have a bitter and citric taste so mixing it with orange juice or lemon water works well.

Serving Sizes: One bag of The Define Booster contains 100 servings if following the above directions. That's just over 14 weeks' worth if consuming daily.

Works Well With: The Tone Capsules to raise your metabolism and support healthy fat-loss.

Giving Back

For every purchase you make with Innermost, we will donate a meal to a child in need.

Innermost is proud to partner with The Akshaya Patra Foundation to provide better nutrition, education and employment levels and end the poverty cycle in India. Learn more here.

Metabolise fat for energy
A weight loss supplement that's science backed. Acetyl l-carnitine helps the body break down fat cells to be used as energy, without any weird side effects.
Improve tone and definition
Use as part of a healthy diet and regular exercise to help you tone up and define.
Support energy and performance
A natural energy booster, acetyl l-carnitine is able to cross the blood-brain barrier to provide mental benefits as well as physical.
Easy to use
Simply add to smoothies, porridge, your protein shake, or have on its own, for an immediate nutrient boost.

User trials

*Results based on 59 participants surveyed over a 30 day period. Participants were requested to log a diary and complete a survey at the end of the month.

I’ve never been able to see muscle definition…

Gaining definition can seem like an unattainable goal. 

But it doesn’t have to be. If you’ve been working hard to see results, and just want an extra push in the right direction, then look no further. 

The Define Booster is one of our most popular products for a reason. Formulated by leading nutritionists, it's been crafted to metabolise fat for energy, support endurance, and even boost memory and learning. Start seeing the lean muscle definition you’re looking for. Because reaching your fitness goals doesn’t have to be impossible.

Do I have to take it alongside a workout?

You don’t have to be working out to take The Define Booster - you can take it whenever you want, even on non-workout days.

What does The Define Booster taste like?

The Define Booster has a tart, almost citrusy flavour (naturally). Think lemon water.

Can I mix it with other products?

You can absolutely take The Define Booster alongside any other Innermost product, though due to its tartness we’d recommend having it separately in a glass of cold water with a squeeze of lemon juice.

Why should I believe this product will work?

All our products have been formulated by expert nutritionists using science-backed research supported by peer-reviewed clinical trials. You can read some of these clinical studies by clicking here. Our products work because we focus on the following things above all else - the ingredients we use, the quality of these ingredients, their concentrations and how well they're absorbed by your body. Our unwavering commitment to that approach means what you get are the highest quality, cleanest supplements in the world today - without any BS.

Innermost is awarded The Game Changer Award. The sands are shifting in the supplements industry. One brand stands out most, Innermost. We now expect more from our supplement products and Innermost is well ahead of the curve.

Science over hype


With so many “miracle” ingredients being touted out there, it can be hard to know what really works. We believe evidence-based ingredients are the best way to better health. With decades of clinical studies showing how the active ingredient in this product can encourage the metabolisation of fat during physical activity, ensure efficient use of energy, and help improve tone and definition, we're confident that you’ll thank us later.

Per Serving:

Acetyl L-Carnitine

Acetyl L-Carnitine (2g): One of the most popular non-stimulant fat-loss supplements on the market today. A non-essential amino acid found naturally in the human body, necessary for transporting fat to the body’s power-generating mitochondria for use as energy during physical activity. Without carnitine, we wouldn’t be able to use fat effectively as a source of energy, which could result in the body having to break down muscle instead. The key benefit of the acetyl form of carnitine is that it can cross the blood-brain barrier to improve mood, learning and memory as well. References > 1, 2.

Allergens: None. 

Learn More:  6 Habits to Melt Fat Fast
Learn More:  5 Reasons Why You Aren't Getting Leaner

Why it's special

Acetyl L-Carnitine

Acety l-carnitine is a substance natural to the body that serves an important role in the burning of fat for energy, and ferrying fatty acids across the walls of the mitochondria, where they are oxidised and turned into energy. On its return trip from inside the mitochondria, it brings back acetyl groups and other small fragments produced in fatty acid oxidation. Carnitine's role in fat metabolism leads it to affect, in some degree, all the other energy metabolism in the cell, including the burning of carbohydrates. Some researchers have suggested that its important role in the burning of fat also makes it useful in diets for weight loss.

When should I use the product?

The Power Booster anytime during the day or before your workout.
The Energy Booster right before and/or during your workout.
The Detox Booster works well as a morning/afternoon pick-me-up.
The Define Booster anytime during the day but morning works well.
The Glow Booster anytime during the day but morning works well.

How many servings do I get?

Based on taking each product every day as recommended:

The Power Booster will last 60 days.
The Energy Booster will last 30 days.
The Detox Booster will last 60 days.
The Define Booster will last 100 days.
The Glow Booster will last 20 days.

Can I mix and match products?

Yes, absolutely. We developed all our products so that you can mix and match any of them depending on your individual goals and needs. You will get the benefits of each of them regardless of whether you're taking them alone or with any of our other products.

What sort of testing do you do?

We go over and above to ensure you get the best quality and safest products possible. We only use ingredients that have a visible supply chain, and our manufacturing facilities are approved to the highest regulatory standards. Once we receive ingredients, we batch test every single one before it gets approval to go into the manufacturing process. That isn’t technically an official requirement but it’s something that we think should be.

Ready To Buy

Customer Feedback

We reached out to the Innermost community to get thier honest feedback on this product. This is what Shiv had to say...

1 Week
1 Month
3 Months

Customer Feedback

Customer Reviews

Based on 21 reviews
Megan Carter
great product!

Honestly, since I am not a fitness buff, I am only going to comment on the taste.... but yes it is lemony.... but it goes SO well with the vanilla vegan protein powder I put in my smoothies. I find the vanilla too sweet, but combined with this - it seems to even out the flavour. Very happy with both products

Julie Smyth
Define, Recovery & Shake bottle

Products ordered and received the very next day. I add rhe define to my post run shake and although it smells quite strong it cannot be tasted in the drink . The recovery tablets are easy to swallow and I also take these post run . I have only been taking these for 1 week and today I was asked if I had lost weight 😍
The shaker is excellent quality with a large drinking spout which I prefer and it has gone everywhere with me since I received it!
Excellent service and products I will certainly be ordering again.

Julie, what a kind and wonderful review thank you so much! So glad you're loving your products.

Much Better Taste

Tried this product 18months ago and just reordered again and the taste is much better, less bitter and easier to digest with water. Haven't used it for long enough yet to see any significant effect just yet.

We listened to your feedback because we're always trying to be better for our customers! Please keep us posted on your results on hello@liveinnermost.com

Chloe Elliott
Great product!

I have had so many mixed experiences buying l-carnitine, where it comes crystallised or is just ineffective. This is one of the best I have tried. Effective, beautifully soft, easy to mix powder and most importantly, great results!

Thanks for the lovely review Chloe! We're very proud of the quality of our ingredients so it's great to hear this.

Great product to mix into smoothies

Great product, doesn't taste brilliant on it's own but it's easy to mix into smoothies and porridge.

Ready To Buy
"Innermost protein is as smart as it is delicious."
"Known for their tailored nutrition for body and mind."
"Favoured by athletes across the globe."
"The best protein shakes for a post workout pick me up."
"Known for redefining performance supplements into cleverer supportive measures."
"You'll have to take our word that it's hands down delicious."
"Filled with all the good stuff... Oh, and it tastes great too."