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USN Diet Fuel Ultralean

USN Diet Fuel Ultralean is claimed to support long lasting, healthy and safe weight loss thanks to its combination of ingredients. However, scientific evidence in support of these claims is lacking.

Below we have reviewed USN Diet Fuel Ultralean against our review criteria to help consumers make an informed decision.

USN Diet Fuel Ultralean Review

USN Diet Fuel Ultralean Pros
  • Contact details are available for the company
  • Product is sold by a selection of high street retailers
USN Diet Fuel Ultralean Cons
  • Evidence of clinical testing on product not readily available
  • Not all of the ingredients have been proven to aid weight loss

USN Diet Fuel Ultralean is marked as ‘Rejected’ as it fails to meet all of the points on our ‘Approved Criteria’. To find out more about how USN Diet Fuel Ultralean performed against our criteria click here.

USN Diet Fuel Ultralean Review

Diet Fuel Ultralean is a health supplement that is easy to take in the form of ‘smooth and tasty’ shakes and is claimed to carry no side effects while working to suppress appetite and speed up the body’s metabolism.

Claimed Weight Loss Benefits
USN Diet Fuel Ultralean claims to be an appetite suppressant and metabolism booster.

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How USN Diet Fuel Ultralean Works


USN claims that their Diet Fuel Ultralean product is able to support long lasting, safe and healthy weight loss due to its specially created formula. The product is claimed to be able to suppress hunger pangs, making the consumer feel fuller for longer, whilst also supplying the body with amino acids (from the protein ingredients) and increasing metabolism. By targeting each of these areas, the official website claims that consumption should result in weight loss and development of muscle.

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USN Diet Fuel Ultralean Key Ingredients

Whey Protein

When used as a meal replacement, whey protein can supposedly help to promote weight loss. It can replace a carbohydrate- and calorie-rich meal meaning that you take in fewer calories and so may be able to burn more fat for energy. It is also sometimes used as an appetite suppressant with the aim of leaving you feeling full and less likely to eat between meals or over-eat during them.


Maltodextrin can supposedly act as an appetite suppressant, again decreasing the amount you eat at meals and reducing the need to snack. It is also thought that the substance is able to speed up the body’s metabolism.


Also known as vitamin B2, riboflavin is understood to assist the production of energy in the body by aiding the metabolism of carbohydrates, proteins and fats, which, in turn, is thought to allow energy to be stored in the muscles.

Folic Acid

Folic acid may help to maintain stable levels of insulin in the body along with some vitamins (such as vitamin C and vitamin B3). Keeping your blood insulin levels constant is believed to be important for efficient fat burning as it supposedly allows the body to burn fats immediately instead of storing them.

Calcium Caseinate

Calcium caseinate is a protein that is extracted from the insoluble portion of milk before being purified in a chemical process. The substance is able to release proteins at a slow and steady rate and is popular amongst bodybuilders as this means that it may be able to provide helpful muscle building amino acids for longer than other proteins.

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USN Diet Fuel Ultralean Clinical Studies

Clinical Researcher 538

Clinical studies are important when it comes to health supplements as they are able to highlight any safety concerns and prove whether or not a product works. USN states that their products are well tested but evidence of these tests does not appear to be readily available to the public. However, there is evidence of clinical testing on some of the ingredients that are found within the supplement.

Clinical Studies on the Ingredients

Whey Protein

In a randomised, double blind, parallel arm, 12-week study, subjects consumed whey protein 20 minutes before breakfast and 20 minutes before dinner. The body fat and the lean muscle tissue of the subjects were measured throughout the trial, and body weight and anthropometric measurements were recorded every 4 weeks. The results of the study showed that those subjects taking the substance lost a greater amount of weight than those that were not.

In another study, 73 obese or overweight subjects took part in a double blind, calorie controlled trial over the course of 23 weeks. The study found that increasing the amount of whey protein in the diet of subjects caused a reduction in the amount of body fat.


In a study conducted by scientists in order to test effectiveness of riboflavin in migraine prophylaxis, it was found that the vitamin is able to cause significant changes in weight loss when taken in small amounts each day. There were no reports of any side effects to taking the substance in this trial.

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USN Diet Fuel Ultralean Side Effects


There is no mention of any side effects of Diet Fuel Ultralean on the USN website; however, some of the product’s key ingredients carry potential side effects that some people may experience. These effects include increased bowel movements, flatulence, bloating, fatigue, headaches and nausea.

Some of the ingredients are also known to react with some medications, such as antidepressants, as well as some medical conditions like heart conditions. It is not known for certain whether the supplement is suitable for pregnant or breastfeeding women and so for this reason they are advised not to use it.

Side Effects associated with the Ingredients

Whey Protein

Whey protein is reported to increase bowel movements in some people as well as potentially causing nausea, thirst, bloating, cramps, reduced appetite, fatigue, and headaches. There is not enough known about the side effects that whey protein may have on pregnant or breastfeeding women and so they are advised not to take the substance; you should also not take whey protein if you are allergic to cow’s milk.


Maltodextrin is not believed to cause any side effects, but be sure to contact a doctor if you notice any changes to your health.

Folic Acid

Folic acid may cause nausea, abdominal cramps, diarrhoea, rashes, sleeplessness, irritability, confusion, stomach upset, behaviour changes, skin reactions and flatulence. Taking the substance for long periods of time or in very high doses may cause some serious side effects such as heart attacks, especially in those who have pre-existing heart conditions, and it may increase the risk of lung or prostate cancer.

Calcium Caseinate

There are no serious side effects known to be associated with this protein, however it is advised that pregnant and breast-feeding women avoid taking the substance and those with kidney conditions should also avoid taking it as it can cause these conditions to worsen.


Riboflavin is able to cause some uncomfortable side effects such as diarrhoea and an increase in urine. It should not be taken in large doses during pregnancy as this may prove to be harmful to the foetus. Large doses of riboflavin can react with antidepressants and drying medications and so should not be taken with these medicines.

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How to Use USN Diet Fuel Ultralean

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The USN website offers clear instructions as to how to use their Diet Fuel Ultralean product as well as highlighting some of the excluded groups – people who should not use the supplement.

For a ‘smooth and tasty shake’ the customer is advised to add 2 rounded 55g scoops of USN Diet Fuel Ultralean to 200-300ml of cold water or skimmed milk. You should then mix it thoroughly by shaking the mixture for about 30 seconds. Users are advised to have between 1 and 3 servings per day depending on how many meals or snacks you are aiming to replace. You are able to take the supplement at any time during the day.

Pregnant and breast-feeding women should not take the supplement as some of the ingredients may cause babies harm and not enough is known to deem them safe for their use. Children are also warned not to use the product. The product contains traces of milk, soy, nuts and crustaceans and so people with allergies to these substances should not take the supplement. Those with heart or kidney conditions should speak to their doctor before using the product as some of the ingredients can worsen these conditions when taken in high doses or for a long period of time.

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Who Makes USN Diet Fuel Ultralean?

USN stands for Ultimate Sports Nutrition; the company claims to be a leader in sports nutrition and bodybuilding supplements, supporting their customers in health and muscle gain. Their research and development team supposedly works closely with various international pharmaceutical companies to ensure continuous product enhancements and to uphold quality control.

The company website appears to be professional and provides an address in Bromsgrove and a customer service telephone number meaning that customers are able to contact the company easily should they have any queries. The company’s products, including USN Diet Fuel Ultralean, are stocked by several major UK high street shops including Tesco, Holland and Barrett, and Boots, which would further suggest that the company is credible.

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Where to Buy USN Diet Fuel Ultralean


USN Diet Fuel Ultralean can be purchased directly from the USN website for the price of £28.99 for a 1kg tub of any flavour or £51.99 for a 2kg tub. The website offers free delivery on orders over £20 and if you purchase 3 or more products you are able to receive a 20% discount. Signing up to the company’s newsletter also means that you are entitled to 10% off all purchases.

The supplement can also be bought from many UK high street shops such as Tesco, and Holland and Barrett. From Holland and Barrett, you can purchase 1kg of USN Diet Fuel Ultralean for £27.99, which is slightly cheaper than the official website. Tesco sells 1kg of this product for £28.

Amazon sells both the 1kg and 2kg tubs; you can buy the 1kg from £19.89 to £21.69 depending on flavours. You can also buy the 2kg tub for £34.99, which is a significant saving compared to the official website. The product is also sold by Amazon, which makes it safer for the customer.

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Does USN Diet Fuel Ultralean Meet our Approved Criteria

Money-back-guarantee: There is no mention of a money-back-guarantee.

One-off payment: Yes, £14.00 for 500g, £28.99 for 1kg, or £51.99 for 2kg.

Manufacturing Standard: Not disclosed.

Accompanying Diet Plan: No, but they do offer some recipe ideas.

Ingredients and quantities disclosed: Ingredients are revealed, but not quantities.

Company contact details readily available: Yes – an email address, postal address, and phone number.

USN Diet Fuel Ultralean does not meet our ‘Approved’ criteria as the website fails to disclose ingredient quantities and the company does not offer a money-back-guarantee.


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Overall Verdict

To conclude, USN Diet Fuel Ultralean is a supplement that, according to its positive customer reviews, works to aid weight loss by boosting metabolism and suppressing hunger. The supplement is widely available to purchase both online and on the UK high street. There are no reports of any serious side effects from either the product itself or its key ingredients and clinical testing supports this, but suggests that the product may react with some medicines and medical conditions. Unfortunately clinical evidence is not available to support the weight loss effects of all of the ingredients in the product.

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3 responses to “USN Diet Fuel Ultralean”

  1. Margaret Semple says:

    I tried a sachet of Diet Fuel Ultralean Vanilla for breakfast this morning and found it very tasty and very filling. I made it with skimmed milk in a blender for 30 seconds (as instructed) and there were no lumps. I did experience the ‘increased bowel movement’ side effect but this would not stop me from buying the product.

  2. Mariaan says:

    Can you take The Ultalean shake for any meal replacement

  3. Mrs Campbell- harris says:

    We are a month into using meal replacements and are very happy with the product, however we bought the banana and caramel shake which is having really dire results. Both my husband and myself have such bad wind and diarrhea we can hardly leave the house. As we bought a large vanilla at the same time could we mix the two which would hopefully dilute the effects of the other one? None of the other shake products have had this effect on either of us ,so is there something different with the caramel one?
    We are finding the shakes very filling and we are enjoying using these products, so Iare there any other shakes that we need to avoid ?

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