Whey Protein for Weight Loss

Last updated July 24th 2015

Whey protein is a popular ingredient in weight loss shakes; it has been shown to help to build muscle but evidence in support of its potential weight loss properties is less conclusive.

Though originally best known for use in protein shakes designed for bodybuilders, whey protein has become a popular addition to weight loss supplements (particularly shakes) in recent years.

The ingredient is a strong source of amino acids and has been shown in clinical studies to help with the construction of muscle. It is generally considered to be safe for consumption, although some people may experience gastro-intestinal side effects.

Here we will discuss what whey protein is and precisely how it is thought to aid weight loss. We will then find out whether or not these claims are backed by scientific evidence and discuss whether the ingredient would be suitable for you.


What is Whey Protein?

Whey protein is created as a by-product of the process of cheese-making. Milk becomes coagulated in this process, leaving behind the whey which includes all of the aspects that are soluble after the pH is reduced to 4.6. Whey contains 5% lactose, which is the main sugar found in milk, as well as a selection of bacteria and minerals. The whey can then be dried and the fats can be removed in order to make a purer form of whey protein which can be used in supplements and for foods.

The protein is made up of a great array of amino acids – these substances are known as the building blocks of proteins and so carry a number of important functions within the body. These functions include growth, muscle growth, and muscle repair, amongst others.

Besides being used as an athletic and bodybuilding supplement, whey protein is sold as a replacement for milk in those who are lactose intolerant and for boosting levels of glutathione in those who have HIV. It has also been said in the past that whey protein can help with the treatment of a selection of health conditions, including asthma, allergies, lung disease, eczema, osteoporosis, cancer, and high cholesterol. It is also believed by some to help to boost weight loss.


How does Whey Protein aid Weight Loss?

Whey protein is regularly stated to help people to lose weight and in turn, is often added to weight loss and dieting products. Some people believe that the ingredient is thermogenic. This means that it induces the process of thermogenesis – increasing the internal body temperature. Increasing the body temperature is said to have a beneficial effect for weight loss; it is thought to provide a more optimal environment for cells and enzymes to work in.

As such, thermogenic substances are believed to have the potential to increase the speed of fat-burning enzymes that are involved in lipolysis (the breakdown of lipids), and increase the activity of numerous cells in the body – thus making them burn more calories for energy. These processes are known as fat burning and metabolism boosting consecutively.

Others have stated that it also has an appetite suppressing effect. The protein is thought to help to keep you fuller for longer, thus preventing snacking between meals. This can be said for any type of protein, not just whey protein. Appetite suppression can be a useful property of a weight loss supplement, particularly for individuals who are trying to follow a portion-controlled diet.

Finally, it is thought that whey protein may be able to help with weight loss because it is an important component in the synthesis of new muscle. If combined with regular exercise, consuming whey protein may help to increase the amount of muscle gained. As described on the NHS webpage on metabolism, muscle has the potential to burn more calories than fatty tissue at rest and as such, increasing the amount of muscle that you have could help to increase your metabolism (or resting energy expenditure; the amount of calories that are burned for energy when the body is at rest).

Depending on which source you are looking at, therefore, whey protein may be claimed to tackle three of the five key areas of weight loss. These are: fat burning, metabolism boosting, and appetite suppressing.

Whey Protein Clinical Studies

Whey protein has been the subject of a number of clinical studies that have tested its effects on many different bodily functions. Of interest here, are those that have been undertaken in order to determine whether or not the substance can aid weight loss. We will look at those that have been performed directly on whey protein and weight loss as well as those that have looked at whey protein and athletic performance as exercising aids weight loss in itself, but may also increase muscle mass which could help to boost the metabolism in the long-run.

A clinical study is a trial that is undertaken by scientists in an attempt to test the effects and/or safety of an ingredient or a product. These trials are performed under controlled conditions, and may be done on individual cells, small mammals, or humans. The most reliable studies are those that are performed using large groups of human subjects and randomised, double blind, placebo-controlled methods. In order to be deemed reliable, a study must be published in a scientific journal; this ensures that the study has used strong methods and is a fair test.

Whey Protein for Athletic Performance Clinical Studies

Since whey protein is most commonly used as a dietary supplement for athletes and bodybuilders, there have been a great number of scientific studies into its potential effects in these areas. A small selection of these trials will be summarised below.

One study, published in 2006, was performed to test the effects of whey protein on strength and body composition. The authors looked at hydrolyzed whey isolate and casein and tested their impacts during 10 weeks of resistance training. Thirteen male, recreational bodybuilders were involved in the double-blind trial. Measurements were taken in the week before, and the week after the 10 weeks of resistance training. The results indicated that subjects who were taking the whey isolate had a much greater lean mass gain than those who were taking casein; a significant change in fat mass was also reported. Moreover, those in the whey isolate group had greater improvements in strength than those in the casein group.

A second study was undertaken to compare the effects of a soy product and a whey product. Eighteen male subjects who belonged to a university weight training class took part in the trial; they were given protein bars to consume each day that contained either soy or whey protein for a period of nine weeks. The whole group continued to train throughout the trial, including the control group who did not consume a protein bar. The results suggested that the consumption of both soy and whey can increase lean body mass when compared to placebo. It was however also noted that the whey and placebo group showed a potentially negative post-training effect on two antioxidant-like functions, whilst the soy group did not.

The final study that we will discuss tested the effects of whey protein isolate consumption on muscle proteins and recovery from muscle damage. Seventeen healthy but untrained males were involved in this trial. The subjects were divided into a whey protein isolate group and a carbohydrate group. The treatments were consumed five times a day for 14 days after a contraction-based resistance exercise session. At three and seven days into the recovery period, knee extension strength was significantly higher in the participants who had been taking whey protein. It was concluded that whey protein supplementation may help in recovery from muscle training.

Whey Protein for Weight Loss Clinical Studies

Unlike many ingredients that are common to weight loss supplements, the potential effects of whey protein on weight loss have also received a fair amount of clinical attention. Again, a number of studies have been performed on the subject, only a small selection of which will be discussed here.

A study published in the British Journal of Nutrition investigated the effects of whey protein on a number of parameters associated with weight, including body composition, blood glucose levels and lipids. The substance was tested against casein and glucose which acted as a control. Seventy individuals were involved in the 12 week trial, all of whom were overweight or obese and had a mean age of 48.8. The subjects were randomised to receive whey protein, casein, or glucose in a parallel design. The results showed that those who were consuming whey protein did not show a significant difference in body composition or blood glucose after the trial when compared to the other groups, but did have significantly lowered TAG levels, total cholesterol and LDL cholesterol. Fasting insulin levels were also reduced with the consumption of whey.

A 2011 study tested the effects of whey protein, soy protein and an isoenergetic quantity of carbohydrate on body weight and composition. The double-blind study was undertaken using ninety obese and overweight subjects. The subjects were divided into three groups and each consumed the supplement (whey, soy, or carbohydrate) twice a day in beverage form. After 23 weeks, those in the whey protein group had significantly lower body weight and fat mass measurements than those in the carbohydrate group. Waist circumferences were also reduced in the whey protein group.

Another study, published in 2008, reported similar results. For this trial, a specialised whey fraction was used that is called Prolibra. The subjects all consumed a very-low calorie diet for twelve weeks and those consuming Prolibra took it in beverage form 20 minutes before breakfast and 20 minutes before dinner for 12 weeks. By the end of the trial, both groups had lost a significant amount of weight; those taking Prolibra did lose more weight, but this result was not significant. Subjects in the Prolibra group did however lose significantly more body fat than the control group and lost significantly less lean muscle mass.

Finally, a study was performed to test the effects of whey protein on insulin sensitivity and body weight in rats. The rats were given a high-fat diet for nine weeks, after which time they were divided to receive either 80 or 320g protein/kg diet provided by either whey protein or red meat, for a further six weeks. The high dietary protein was seen to reduce energy intake and visceral and subcutaneous fat. The consumption of whey protein (not red meat) was seen to reduce body weight gain by 4% and also to reduce blood insulin levels by 40%. It was concluded that whey protein is more effective than red meat at aiding weight loss and insulin sensitivity.

Side Effects of Whey Protein

Generally speaking, whey protein is safe for consumption by most people and is unlikely to cause side effects. If taken in high doses however, it is possible that the substance will cause side effects, primarily associated with the gastro-intestinal tract. These include, for example, stomach cramps, bloating, increased bowel movements, and nausea. People have also reported experiencing thirst, reduced appetite, headache, and tiredness with the consumption of whey protein.

If you experience any severe side effects, or any mild side effects for long periods of time, then it is always best to stop taking the supplement and consult a doctor.

Is there anybody who shouldn’t take Whey Protein?

It is recommended that you avoid taking whey protein supplements if you are pregnant or breastfeeding. No evidence is available that it could harm the mother or baby, but not enough studies have been performed to guarantee that no harm will be done. Whey protein may also be unsafe for those who are allergic to cow’s milk.

The ingredient may interact with certain kinds of medications. If you are taking any form of medication, it is recommended that you consult a doctor before taking whey protein supplements. WebMD warns that whey protein can reduce the amount of levodopa that the body absorbs, thus possibly reducing its effectiveness. You should not take whey protein supplements if you are prescribed levodopa. Similarly, whey protein may reduce the amount of alendronate and antibiotics that are absorbed by the body. It is recommended that you avoid taking whey protein supplements within two hours of taking these medications.

Whey Protein Products

Whey protein is regularly sold on its own in powder form, or can be found as an ingredient in a weight loss, bodybuilding or athletic supplements. It is fairly easy to get hold of on the UK high streets and can be found in well-known retailers such as Holland and Barrett. Online retailers also sell whey protein both on its own and within other products; examples of online companies that sell whey protein products include MyProtein and GNC. Prices will vary between retailers, but typically a bag of whey protein powder will cost around £15 for 1kg.

Different products may contain different concentrations of whey; this information may be provided in grams or as a percentage per serving. It is also possible to find a great selection of flavoured whey products as well as food items, e.g. snack bars, that have been supplemented with whey protein. Retailers recommend taking whey protein after a workout. The usage instructions are usually fairly similar – the whey protein powder can be mixed with water or milk to make a shake, or it can be added to a smoothie or even porridge.


Whey protein supplements may be incorporated into the diet by a range of different people, including athletes, bodybuilders, and those who are just looking to lose some weight. It is usually taken in the form of a shake and is readily available from health retailers. Whey protein is generally safe for consumption by most people, although it may cause some gastro-intestinal side effects and is not suitable for those who are allergic to cow’s milk. Scientific studies have indicated that the substance may have the potential to increase muscle mass, improve recovery time from exercise and improve body composition and fat loss, though results have not been entirely consistent. In order to get the best results, it is recommended that whey protein is taken alongside regular exercise.