Best Protein Shakes for Weight Loss

Last updated October 26th 2015

Protein shakes have become very popular in recent times, perhaps due to the great selection of different products available for consumers to purchase, but also their convenience.

Protein is the key source of growth and repair in the human body. Whilst common animal sources of protein include: meats, fish, eggs, and other vegetarian options such as pulses and cereals – the use of protein shakes are something considered by many.

In this article, several types of protein shakes will be described, and their effectiveness in weight loss studies analysed, as well as the safety of these.

The recommended intake of protein set by the British Nutrition Foundation is currently 0.75g of protein per kilogram of bodyweight for adults. For example, according to the ONS, the average UK male weights 83kg (13 stone) and would therefore require around 62g of protein each day. Whilst studies have shown that protein helps to build muscle, does it help to lose weight?

How Protein Shakes Aid Weight Loss

Protein shakes are thought to tackle three of the five main areas of weight loss – these include: fat burning, metabolism boosting, and appetite suppressing.

High protein diets are thought to promote increased energy expenditure through thermogenesis. Previous studies (for example here and here) have shown results that suggest that proteins generate a larger thermic effect of food than carbohydrates or fats – this means that protein burns the most calories after you eat it.

During weight loss, high protein diets have also been suggested to prevent a fall in resting energy expenditure. The way in which protein is thought to preserve resting energy expenditure/keep metabolism high is by retaining lean mass – the more protein you eat the more likely you are to hold on to existing muscle. The more muscle you have, the more calories the body is able to burn.

There is also some evidence to suggest that protein helps to suppress appetite. It is thought that consuming a high protein diet can lower the concentration of the hormone ghrelin, which depends on food intake and therefore plays a vital role in appetite. These will be discussed further in the clinical studies section.

Meal-Replacement Protein Shakes

Meal replacement shakes often contain a relatively high source of protein, as well as carbohydrates, fibre, and vitamins. Instead of supplying the body with the nourishment from foods, users can mix them with water or milk and consume them as a beverage. Since they replace the need for a meal, they can contain anywhere in the region of 300 calories per shake, but many products will be different. Some people may find these type of protein shakes convenient because the user only needs to mix it with water and therefore does not need to think about what food to eat. It also eliminates the need to count calories, as this will be stipulated with the product. 

With regards to clinical studies, there is some evidence to support high-protein diets for weight loss. For example, the results from one study, suggest that a high protein diet helped subjects to lose less lean body mass than those receiving more normal protein diets. Another study, that looked at the long-term effects of a high protein diet concluded that they appeared to have some weight loss benefit. Furthermore, one paper, which reviews six studies on meal replacement, finds evidence supporting the role of meal replacement products in weight loss, with no side effects. The results from another study reflect that meal replacement shakes are as effective as a structured weight loss diet.

Key Ingredients in Protein Shakes for Weight Loss

Three common forms of protein shakes are whey, casein, and soy. Whey protein comes from the watery part of milk that is separated from the curds in cheese production. This usually comes in two forms: isolate and concentrate. Whilst some of the fat and lactose is removed from concentrate, isolate undergoes a more strenuous process, removing a more significant amount of fats. This is why isolates are the purest form of protein – generally considered to contain a protein concentration of 90 percent or more

Soy is arguably the most common plant-based protein source. This derives from the soybean, most commonly consumed in Asian countries such as China. Casein is the main protein in milk, representing around 80 percent of the total, where whey constitutes the remaining 20 percent. For more information regarding the three main types of protein, please refer to this published paper from 2004.

Other ingredients that are commonly added to weight loss protein shakes may include green tea, caffeine, carbohydrates, and vitamins. Green tea and caffeine may be added under the premise that they can help to provide an energy boost and increase weight loss. Green tea has been shown to have fat burning properties, and studies have indicated that caffeine may have an impact on metabolism. Results of studies on these ingredients have overall been inconclusive however, and more research is required before it can be stated that they have the potential to aid weight loss.

Clinical Studies

Clinical studies are performed by healthcare professionals to determine the efficacy and safety of the wide range of supplements available for consumers to buy. To be able to infer things from studies, it is generally accepted that they should be undertaken in a controlled setting. Research is essential in identifying new treatments, or to challenge current thinking. Without this, consumers may do harm to themselves by taking certain supplements. There are numerous studies that have been conducted on high-protein diets, where as much less is available in relation to protein shakes.

Clinical Studies on Protein Shakes for Body Composition

One published study from 2008, aimed to assess the effect of a protein supplement on weight loss. One hundred and four individuals took in this trial, who were split equally into a control group, or a treatment group. During the study, the subjects consumed 500 calories per day for twelve weeks. At each four-week interval (from 0 – 12) measurements were recorded such as body weight and waist and hip ratios. The results showed that while both groups lost weight, and the treatment group lost more weight than the control group, the differences were not significant. Yet, the authors concluded that since subjects in the treatment group lost 6.1 percent of their body fat mass, and as a 5 percent reduction in body fat mass has been associated with reducing the risk of obesity-related diseases, these results have some significance.

Another study published in 2009 examined the effect of a protein supplement on strength and body composition. Thirty-three males took part in this experiment where 13 where assigned to the first treatment group who received the protein supplement in the morning and evening, another thirteen who received the same supplement immediately before and after workouts, and the final seven who served as the control group. Whilst each group saw a significant effect in their strength (from week 0 to week 10), there were no significant effects between the groups. Additionally, no change in body mass or percentage of body fat were reported in any of the groups. The authors concluded that their results suggest the timing of a protein supplement did not provide any benefit to strength or body composition.

Clinical Studies on Protein Shakes for Appetite Suppression

One recent study, published in 2004 aimed to compare the effects of whey, soy, and casein protein on food intake and energy expenditure. Twenty-four subjects took part in this trial, all of who were of normal weight. The subjects were split into either one of the three treatment groups where they ingested whey, soy, or casein protein for breakfast, or the control group where they received a placebo – this was undertaken for four, seven-day sessions. Many interesting results were recorded such as casein consumption appeared to lead to a lower energy intake than the whey group; soy protein resulted in higher thermogenesis than the control group; and respiratory quotient was lowest in the whey group, compared with the control and soy groups. The authors concluded that their results suggests consumption of the three different proteins lead to distinct but differing effects on thermogenesis, fullness, and respiratory quotient.

Another published study from 2011 investigated the effect of different proteins on food intake and satiation. In the first experiment, the effect of 20g of casein, whey, pea protein, egg albumin, maltodextrin, or a placebo containing water, on food intake half an hour later. In the second experiment the effect of 20g of casein, whey, pea or a water control on satiation was analysed. Both experiments were conducted on thirty-two male volunteers. The results showed that food intake was significantly lower after the casein or pea proteins relative to the placebo. Similarly, the feeling of fullness was significantly higher after the casein and pea proteins. The authors concluded that casein and pea proteins appear to have a stronger effect on food intake compared with whey, therefore are strong candidates for satiety.

Other studies have shown similar results to that above (a similar or lower effect on food intake), but when whey is compared to casein. For instance this study showed that energy intake from a meal was significantly less 90 minutes after a preload containing whey, compared with casein. Where as this study’s results suggest that energy intake and appetite were equally reduced after consumption of whey or casein, relative to a glucose control.

Differences in results among studies could be due to many reasons such as methodology, sample size, and dosage.

Side Effects of Protein Shakes

Whey protein is usually considered to be safe for the majority of people when consumed orally. High doses may cause side effects including nausea and reduced appetite. Soy protein is also thought to be safe when consumed in small doses, however mild side effects may include constipation and nausea. Further research is needed to determine if casein is safe in diet supplements.

A high protein diet remains a risk to people with pre-existing renal disease, the current literature however, reviewed here, does not find any sufficient evidence to suggest a link between protein intake and renal disease in healthy individuals.

Another paper, which largely agrees with the one mentioned above, that there is no clear link between high protein diets and renal related problems in individuals with healthy kidneys – the author does point out however that high protein diets may cause harm for those with chronic kidney disease. As this is often unnoticed (silent disease), individuals should undergo a screening before starting this type of diet.

Another paper which reviewed the American Heart Association’s claim that individuals on high protein diets are “at risk of potential cardiac, renal, bone, and liver abnormalities” found that there was little if any scientific evidence to support any of their claims. Whilst current studies have not identified any side effects, further research should monitor this situation.

Who Shouldn’t use Protein Shakes?

It is recommended that those individuals who are pregnant or breast-feeding do not consume protein shakes. Some of the proteins mentioned in this article contain milk so individuals with a milk allergy should also be careful. People with pre-existing medical conditions should consult their doctor before using.

How to Choose a Good-Quality Protein Shake for Weight Loss

The first consideration one may like to make is whether the firm you are purchasing from are reputable. By researching the company website you can save yourself in the long run: common things to look for would be whether a company address is listed and exists, a telephone number, or customer email address. Secondly, does the company provide lots of other products, and are customer reviews generally positive on the whole? Do the products meet certain quality standards? Formal standards to look for here are ISO 9001, Good Manufacturing Practice (GMP) and Hazard Analysis and Critical Control Point (HACCP).

In relation to the protein shake itself; another suggestion may be to look for a protein shake that contains a relatively high concentration of protein. A quick Internet search reveals that one specific whey isolate protein contains 22g of protein by 25g serving. As mentioned in the section on different protein types, whey isolate is the purest form so this may be an option.

It may also be beneficial to avoid products that contain ingredients that are banned by the Food and Drug Administration (FDA). DMAA, for example, can still be found in protein shakes available online, but may pose a serious health risk.


Protein shakes are becoming increasingly popular for weight loss as well as muscle building and recovery. Clinical studies have shown that protein supplementation may help to improve body composition and suppress the appetite. Which type of protein shake you opt for will largely depend on your goals and your health, as well as any dietary restrictions. Protein shakes vary greatly in the quantities of protein, carbohydrates, and fats, as well as in the main sources of protein and addition of herbal ingredients, such as caffeine and green tea. It is important that you purchase a protein shake from a reliable source.