Protein World Slender Blend

Last updated January 7th 2016

Protein World Slender Blend claims to target weight loss and includes lots of vitamins and minerals; however, there are concerns about the product’s caffeine content.

Protein World Slender Blend Pros

  • Full ingredient quantities revealed
  • Some of the ingredients have been the subject of clinical studies

Protein World Slender Blend Cons

  • High caffeine content, particularly in the capsules
  • Website makes unsupported claims
Protein World Slender Blend is a meal replacement shake developed by Protein World. The website claims that this product is low in calories and high in proteins, while its main benefit is said to be weight loss.

The company behind the product specialises in health products that contain high amounts of protein. The company claims that Protein World Slender Blend has been used by leading health professionals from all over the world.

The product comes in two forms, both of which contain caffeine; there are some concerns for those who are sensitive to caffeine. The site’s claims about what this product can do are unsupported.

Protein World Slender Blend Review

In this review of Protein World Slender Blend, we will look at how Protein World Slender Blend works, its ingredients and clinical studies. We will also examine the possible side-effects of taking Protein World Slender Blend. This review should help you decide if Protein World Slender Blend is the best product for you.

Approved Choice

Nutribuddy Sculpting Whey

Nutribuddy's Sculpting Whey shake is marketed as a delicious shake to help with weight loss, toning and definition.

  • Low calories - 115 per serving
  • Free from side effects
  • Some ingredients proven to help weight loss

How Many of The 5 Key Areas of Weight Loss Does Protein World Slender Blend Cover?

The website does not make any specific claims about which areas of weight loss the product targets. The two forms of the product have active ingredients containing caffeine, which is often claimed to target fat burning and metabolism boosting.

Fat burners trigger a natural process called thermogenesis, which is where body temperature is raised after food has been eaten and calories are burned off. A way to burn off extra calories is to have this process triggered without food being consumed, which is what fat burners do.

When you have a slow metabolism, less calories are burnt by the body at rest, which can lead to weight gain. Giving metabolism a boost results in calories being burned off more quickly. The body uses up stored fat for energy, which can result in weight loss.

Protein World Slender Blend Ingredients

Green tea extract

Green tea is produced when the Camellia sinenis plant leaves are steamed at high temperatures. It contains a lot more antioxidants than the other two main types of tea, black tea and oolong tea, because it does not undergo fermentation, a process which rids tea of a lot of antioxidants. Some of the conditions that green tea is used to treat include heart disease, weight loss, cancer, Alzheimer’s and high levels of cholesterol. It has been used in traditional Chinese medicine for many centuries to treat some of these conditions. This ingredient is found in both the capsules and the powder.

Source: NHS

Guarana extract

Guarana is an Amazonian plant named after the Guarani tribe. The plant’s seeds are used or a variety of different purposes and can be found in different weight loss and energy boosting products, as well as in a number of medicinal products. Guarana is also used in food and drink products as a flavouring agent. Some of the conditions it is used to treat include mental fatigue, fever, heart problems, headache and chronic fatigue syndrome. There are some concerns about long-term usage of guarana because of its high caffeine content. This ingredient is found in both the capsules and the powder.

Source: WebMD

Caffeine anhydrous

Caffeine anhydrous is caffeine without water. It is a white powder that does not have a smell. Caffeine is a central nervous system stimulant and is one of the most popular stimulants in the world thanks to its inclusion in a large number of food and drink products. It is mainly used to perk people up and to make them feel more energetic and alert instead of feeling tired and drowsy. Caffeine can become addictive, though the body can become tolerant to its effects quite quickly. This ingredient is only found in the capsules.

Source: Wikipedia

Yerba Mate Powder

Yerba mate is a plant that is native to South America. It is rich in minerals, vitamins and antioxidants. Its stem and leaves are ground together to produce a tea-like beverage which I consumed throughout lots of countries in South America. Some of the conditions that yerba mate is used to treat include headaches, kidney stones, depression and joint pains. Yerba mate also acts as a stimulant as it contains caffeine. This ingredient is only found in the capsules.

Source: WebMD


Choline is a chemical that is similar in make-up to the B vitamins. It can be produced in the liver and has a number of important roles to play throughout the body, especially in the nervous system. It is used to treat conditions such as liver disease, dementia, depression, Alzheimer’s and memory loss. It can also be used to delay fatigue, so it used by a lot of athletes. This ingredient is only found in the capsules.

Source: WebMD

Alpha Lipoic Acid

Alpha lipoic acid is a chemical that in the 1950s was identified as an important growth factor for a large number of bacteria. It is a naturally occurring fatty acid that can be found in foods such as potatoes, broccoli, liver and kidneys. It has not been confirmed whether alpha lipoic acid can treat any medical condition, however it is still used to treat conditions such as Alzheimer’s, diabetic nerve pain, eye problems that are caused by diabetes and alcoholic liver complications. This ingredient is only found in the capsules.


Cayenne Powder

Cayenne is another name for capsicum, a plant more commonly known as red pepper or chilli pepper. The plant’s fruit contains capsaicin, a chemical that is thought to lessen pain when it is applied to the skin. A form of capsaicin can be found in pepper spray as it causes extreme pain to the eyes. Some of the conditions capsaicin is used to treat include upset stomach, diarrhoea, stomach pains, high cholesterol and numerous conditions related to the blood vessels and the heart. This ingredient is only found in the capsules.

Source: WebMD


Tyrosine is an amino acid which the body produces from phenylalanine, another amino acid. Tyrosine’s main use in the body is to produce chemical messengers, which are used in a variety of different conditions involving the brain and mental alertness. As well as being produced in the human body, tyrosine can be found in wheat, oats, beans and nuts, as well as a number of dairy products. Tyrosine is used to treat conditions such as depression, narcolepsy, ADHD, Parkinson’s and Alzheimer’s. This ingredient is only found in the capsules.

Source: WebMD

How Protein World Slender Blend Works

Fat Burning / Binding

The key active ingredients across the two different versions of Protein World Slender Blend that target fat burning may all be able to contribute to fat burning because they contain caffeine. The ingredients containing caffeine are green tea extract, guarana extract, yerba mate powder and caffeine anhydrous.

The way that caffeine targets fat burning is through the stimulation of the central nervous system in order to increase levels of epinephrine, which is more commonly known as adrenaline and travels through the bloodstream to order fat tissues to begin breaking down. More epinephrine could mean that more fat is going to be broken down.

Fat Burning / Binding Ingredients

Green Tea
Yerba Mate

Metabolism Boosting

As with fat burning, there are four ingredients across the two versions of Protein World Slender Blend that may be able to contribute to metabolism boosting because they contain caffeine: caffeine anhydrous, green tea extract, guarana extract, and yerba mate.

The way that caffeine targets metabolism is by releasing neurotransmitters, which are thought to be able to boost a person’s energy levels and raise their metabolism. Some clinical research has suggested that caffeine can increase metabolism in this way, as will be discussed later in this article.

Metabolism Boosting Ingredients

Yerba Mate
Green Tea

Protein World Slender Blend Clinical Studies

Most diet pills and weight loss supplements do not have clinical studies supporting their weight loss claims. Clinical studies are studies that are carried out by scientists and healthcare professionals to determine how safe and effective whole products or individual ingredients are before they are made available for public consumption. Clinical studies can involve people who take part in studies voluntarily and are therefore free to withdraw from studies at any time and for any reason. Other studies may be based in laboratories.

Clinical Studies On Each Ingredient

Clinical Studies on Caffeine

Caffeine is found the following of Protein World Slender Blend’s ingredients: green tea extract, yerba mate powder and guarana extract. It is also present as caffeine anhydrous, which is caffeine without water. Caffeine can become addictive, though the body has been known to quickly build up a tolerance to its effects. What this means is that caffeine may only be good for short-term weight loss. Most of the clinical studies carried out on caffeine have only looked at its short-term weight loss effects; more studies on its long-term effects are needed as many people use diet pills and weight loss supplements for long-term weight loss.

This study looked at the effects of caffeine on metabolism. The study looked at body temperature and energy expenditure in particular. For this study a group of 12 male participants was recruited and they were asked to consume 150ml decaffeinated coffee either with or without 200mg caffeine. Those who did not consume caffeine did not see much in the way of positive results, while those who did consume the caffeine saw their metabolism boosted by as much as 3-11%.

This study looked at the effects of caffeine on insulin sensitivity. High insulin sensitivity can result in obesity, so by lowering insulin sensitivity, you have a lesser chance of becoming obese. There are 12 participants involved with this study. They were split into two groups: one had caffeine administered intravenously, while the other had a placebo. The results produced from the study showed that caffeine could reduce insulin sensitivity by up to 15% in some cases. What this study also showed was that caffeine is able to increase levels of epinephrine by up to five times; as mentioned elsewhere, epinephrine is associated with fat burning and can help with weight loss when levels of it are increased.

Clinical Studies on Guarana

Guarana contains caffeine, though it has been studied as an individual ingredient. One study in particular produced positive results. This study looked at the short-term potential of a guarana and ma huang supplement for weight loss. For the double-blind placebo controlled study, a group of 67 obese people were recruited. Of these, 35 took the supplement, while the other 32 took a placebo. Though there were 67 participants at the study, after the eight weeks the study went on for, only 48 participants had managed to complete the whole study, 24 from each of the two groups. The results showed that the supplement group had lost more overall body weight and body fat than the placebo group. The ma huang may well have contributed to the results, so it cannot be said that it was guarana alone that contributed.

Clinical Studies on Green Tea

Clinical evidence on green tea’s weight loss properties is mixed. That is to say that green tea is thought to be able to help some with weight loss, but not others. Several studies on green tea were compared and contrasted as part of this review, which was carried out to determine whether green tea could be effective at helping obese and overweight people with losing weight. The results of this review showed that green tea could help with weight loss, though the average amount of weight lost by the studies’ participants was not statistically significant. In other words, the amount of weight loss was not great enough to be able to say that green tea was effective enough at causing weight loss. No effects on weight maintenance were reported.

The purpose of this study was to determine green tea’s effects on weight loss. For this study 100 obese women were recruited. The study lasted for 12 weeks. The women were split into two groups: one group consumed green tea three times each day, the other had a placebo at the same times. According to the results, green tea caused an average weight loss of only 0.3%, which is not a high enough result to be deemed statistically significant. If green tea is to be deemed capable of causing weight loss, the result needs to be a lot greater.

This study was carried out to determine the effects of green tea on weight reduction. A group of 60 obese Thais were recruited and the study lasted for 12 weeks. The participants were split into two groups, one of which consumed green tea, while the other consumed a placebo. Both groups were made to stick to a special diet that was low in fat in order to reduce their daily fat intake. The study’s results showed that green tea was able to cause weight loss through increasing both energy expenditure and fat oxidation. Though the results are positive, it is worth bearing in mind that the diet may have contributed to weight loss as well.

More positive results were produced from this study, which was carried out to evaluate the effects of a green tea extract on fat oxidation and 24-hour energy expenditure. The extract contained a very high concentration of catechin polyphenols and caffeine. There were 10 participants, all of whom were male. There were three points during the study when the participants received caffeine, the green tea extract or a placebo. The results showed that of the three, it was the green tea extract that affected energy expenditure the most.  It was concluded that this was because green tea is effective at promoting both fat oxidation and thermogenesis.

Protein World Slender Blend Side Effects

The Protein World website does not mention any potential side effects associated with Protein World Slender Blend. However, there are side effects associated with the product’s two key active ingredients, green tea extract and guarana extract. Both of these ingredients contain caffeine, which has quite a lot of side effects associated with it. It is for this reason why this product is not recommended for anyone sensitive to caffeine.

Side Effects Associated With Each Ingredient

Side Effects Associated with Caffeine Anhydrous

Caffeine anhydrous is simply caffeine without water. There are a number of side effects associated with caffeine, including dizziness, increased heartbeat, nausea, vomiting, convulsions, headaches, heartburn, sleeping disorders and confusion. One of caffeine’s key properties is that it can become addictive, though the body can adapt to a regular caffeine intake quite quickly. This means that the body can get used to caffeine and that side effects should start to subside after a short while. Those who are sensitive to caffeine are more likely to experience caffeine’s side effects, especially nausea.

Side Effects Associated with Green Tea Extract

It is thought that green tea is safe to consume orally so long as it is only over a short period of time. There are some side effects associated with green tea, including stomach upset and constipation. Liver problems have also been linked with green tea, but these rarely occur. Caffeine is one of green tea’s main components, so green tea is capable of causing all of the side effects that caffeine anhydrous can cause.

Side Effects Associated with Guarana

Because guarana contains a high concentration of caffeine, it is capable of causing all of the same side effects linked with caffeine anhydrous. It is thought to be unsafe to consume guarana over a long period of time because of its high caffeine content. The high caffeine content is why guarana has been linked with caffeine addiction: some people have become addicted to guarana’s caffeine content, then after stopping taking guarana, they have experienced caffeine withdrawal symptoms. Some of the side effects linked with guarana include nervousness and insomnia.

Side Effects Associated with Yerba Mate Powder

Yerba mate contains caffeine, so it is capable of causing all the side effects linked with caffeine anhydrous. Because of yerba mate’s high caffeine content, it is thought to be unsafe if taken in high amounts or if taken over a long period of time. Yerba mate can increase the risk of conditions such as cancer of the mouth, lung, kidney and bladder; the risk is even greater in those who regularly consume alcohol or smoke. It is thought to be safe if consumed orally for short periods of time.

Side Effects Associated with Choline

Though choline is generally considered to be safe, taking it in high doses is thought to increase the chance of getting rectum and colon cancer, as well as less severe side effects such as sweating, diarrhoea and vomiting.

Side Effects Associated with Alpha Lipoic Acid

Alpha lipoic acid is generally thought to be safe to consume, though it can cause skin rashes and nausea. It can lower blood sugar levels, which causes symptoms including weakness, hunger, sweating, feeling light-headed and feeling jittery.

Side Effects Associated with Cayenne Powder

Taking cayenne powder over a short period of time is thought to be safe, however it is thought to be unsafe if consumed in high doses over a long period of time. Some of the side effects linked with cayenne powder include stomach irritation, sweating and damage to the kidneys and liver.

How To Use Protein World Slender Blend

To use the powder version, add 40g of the powder (four scoops) to 400ml glass of water to the water. Stir it together then drink. Instead of water, you can use nut-based milks, such as almond, coconut and hazelnut. This product is claimed to be a meal replacement shake; however the website does not say how many times a day you should take it or what the maximum daily dose is.

To use the capsules, take one capsule in the morning and one in the afternoon with meals for the first week of use. For the second week on, take two capsules in the morning and two in the afternoon with meals. You should not take capsules after 3pm because of their high caffeine content.

This product is not to be used by anyone under the age of 18. Women who are pregnant or breastfeeding are also advised to avoid using this. People with caffeine sensitivity should avoid the product.

Who Makes Protein World Slender Blend

Protein World Slender Blend is manufactured and distributed by a UK company called Protein World, which is based in Surrey. The company claims to be leading a protein revolution, offering high-quality proteins, with products containing no hidden ingredients. All products use proteins and are designed to make you healthier, leaner, fitter and stronger. Products do not include any genetically modified organisms.

The company offers 14 day money back guarantees. Refunds will be given for products that you are not happy with, though you will be responsible for paying posting and packaging. Both unopened and opened items can be returned, though for opened items, you should only have used a few scoops of powder in order to qualify for the refund.

The company attracted a lot of negative criticism in early 2015 because of a poster advert that was deemed controversial. Reviews of the company’s products on Amazon are mixed to average.

Where To Buy Protein World Slender Blend

Protein World Slender Blend is available to purchase from the official website, as well as from Amazon.

The capsule version is available for £22. Each bottle contains 90 capsules, which should last 25 days. The powder version is available for £32 for a 1.2kg bottle £58 for a 2.5kg bag. There are four flavours, strawberry, vanilla, chocolate and banana, as well as naked, which is unflavoured; the price does not change for different flavours. It says the 1.2kg bottle contains 30 servings, though no recommended daily doses are given, so it is uncertain how long a bottle of the powder version would last. Standard delivery is available for £4.99 and delivery is free for orders over £100.

Protein World has an Amazon page where all products are available for the same price as the official website. Protein World Slender Blend is also available in different product bundles.

Overall Verdict

Protein World Slender Blend comes in two forms: powder and capsules. Both forms contain ingredients containing caffeine, which targets two different areas of weight loss. However, the capsules contain a total of four ingredients that have caffeine in them, which is a cause for concern, especially considering the company advises you not to take the product after 3pm owing to its caffeine content. The company that manufactures the product specialises in products high in protein that are claimed to improve your health. The company makes claims about what Protein World Slender Blend can do, though these claims are largely unsupported.

Approved Choice

Nutribuddy Sculpting Whey

Nutribuddy's Sculpting Whey shake is marketed as a delicious shake to help with weight loss, toning and definition.

  • Low calories - 115 per serving
  • Free from side effects
  • Some ingredients proven to help weight loss

Customer Reviews Of Protein World Slender Blend

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Protein World Slender Blend SKU UPC Model
6th August by juliaon Protein World Slender Blend

On my 5th day and no weight loss. I have had dreadful nausea, headaches, rashes and severe indigestion. I changed the way I took the drink and tablets so I drank the shake over 30 minutes rather than straight down. It didn't help. Although, to be fair, I was never hungry. I am having two shakes a day with the tablets and an evening meal. If mixed with water as suggested it is incredibly sweet and unpleasant. You can taste the pretend sugars. With almond milk it isnt much better. It is watery and unpleasant. Only refunded on unopened items.

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7th September 2016 by Tanya

I have been using this product for about 10 months. I have tried vanilla, banana and strawberry and enjoyed all three. I moved to Protein World from ViSalus to get a higher amount of protein in my shakes while still keeping my calories down. I have not felt jittery, dizzy, nauseous or had any other side effects. I have a shake for breakfast with 2 fat metabolizer tabs and 2 hunger busters 1 hour before. I sometimes will have a shake for lunch as well but not every day as I did in the beginning months. These shakes are great to have before an early morning run or workout and help to give me the energy I need. As with all diet supplements you still have to work out in order to loose the weight. Protein World sends a fabulous diet plan along with the shakes and I have enjoyed many of the recipes they provided including ones using the shake such as slender pancakes. I am aware that everyone is different and I would recommend for those just starting with any shake that having a fruit or low calorie item with your shake for the first week may help to subside any of these side effects. Many would attribute the dizziness or nausea to the shake but you have likely by starting the shakes for 1-2 meals a day reduced your calorie intake greatly, reduced your carbs and your sugars and reducing carbs substantially can have many side effects of its own. There are many factors to consider when changing your diet outside of the shake you choose but it is important to find one that works for you. Another great option is Idealean protein shakes for women which has lower calories less carbs and is designed with women in mind.

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