Following a protein shake diet encourages weight loss by curbing appetite and reducing the total calories a person consumes in a day. Although these diets can be effective in the short term, healthcare professionals do not recommend living solely or primarily on meal replacement shakes.

Protein helps build muscle and plays a vital role in cell function across the body.

Protein needs will vary from person to person based on their weight and activity levels. Generally, however, the 2015–2020 Dietary Guidelines for Americans suggest that males over the age of 18 consume 56 grams (g) of protein per day, and that females consume 46 g.

A person can easily obtain this amount from the diet by consuming beans, lentils, nuts, meat, eggs, and dairy products.

Protein shakes aim to provide as much protein as food but with fewer calories. Some can even provide more protein than food. The idea is that replacing meals with protein shakes can improve weight loss and muscle gain.

In this article, we explain how the diet works, ways to follow it safely, and what protein shakes can do to benefit overall health.

a man drinking a protein shake as it is part of his diet Share on Pinterest
Consuming protein may help increase feelings of fullness.

Protein shakes offer more than just protein. Manufacturers typically fortify them with a range of vitamins and minerals. They may also contain fruits, vegetables, and other nutrients.

A 2016 meta-analysis linked protein consumption to increased feelings of fullness. People who include enough protein in their diets may therefore have fewer food cravings and eat less. Some may choose to get this protein through shakes.

The sections below discuss protein in more detail.

Benefits of protein

Most protein-rich foods provide a wide variety of vitamins and minerals. Several of these nutrients — including B-complex vitamins, iron, choline, and zinc — are more difficult to get in adequate quantities from other sources.

Other vital nutrients that some protein-rich foods provide significant amounts of include:

How does protein work in the body?

Protein supports numerous vital functions in the body, including building and repairing the bones, muscles, and skin.

It also helps the body create hormones and enzymes and metabolize vitamins. It is an essential part of a well-balanced and nutrient-dense diet that encourages good health.

Read more about protein here.

Several companies offer diets that mainly feature protein shakes. For this reason, the requirements and offerings of each program vary. Some diets are more extreme, encouraging participants to eat only or primarily protein shakes.

However, the most balanced protein shake diets include protein shakes as part of a diet that is rich in other food sources.

For instance, the diet might recommend replacing one or two meals with a protein shake, then eating one or two different meals that also provide nutritional benefits, as well as snacks.

A well-balanced diet should always include an appropriate amount of protein, nutrient-dense carbohydrates, and healthful fats.

Meal replacement shakes should not completely replace healthful, balanced diets. This is because it is difficult to get every nutrient from a single food source.

Furthermore, a body that does not receive enough nutrients may experience problems with metabolism. This may slow or disrupt a weight loss plan. In fact, one 2015 study found that people who eat a varied diet are less likely to have obesity.

Some protein shakes also use large quantities of sweetener to improve flavor, which can trigger blood sugar spikes.

It is also important to avoid consuming too much protein powder in one day. A 2013 review of studies found that consuming more than the daily requirement of protein may lead to problems in the kidneys and bones, as well as increase the risk of cancer.

A Consumer Reports analysis also found that some protein drinks have unsafe levels of contaminants. Three of the drinks that the consumer watchdog tested had high levels of the following contaminants, among others:

  • mercury
  • arsenic
  • cadmium

People who drink three servings of these drinks each day could experience serious health consequences.

In an additional eight of the drinks tested, lead levels were high enough to need a consumer warning in California.

As nutritional supplements, protein shakes are subject to fewer regulations than medication in the United States. Consumer Reports argue that marketing materials for these products may also be misleading.

Instead of protein shakes, they recommend eating protein-rich foods such as milk, lean meats, and eggs.

Protein consists of amino acids, and the best proteins are "complete." This means that they contain all nine essential amino acids.

Most protein shakes use one or more of the following six varieties:

  • whey protein
  • casein protein
  • egg white protein
  • soy protein
  • plant protein
  • beef protein

To get the most out of a protein shake diet, it is best to talk to a doctor or registered dietitian first. People should only consume one or two protein shakes daily and for a short time only.

It is also best to choose a protein shake that fulfills part of a healthful diet. For instance, a person who does not eat many vegetables might choose a meal replacement protein shake that contains vegetables.

The best way to enhance weight loss when following a protein shake diet is by eating nutrient-dense, low-calorie foods between shakes. Eggs, lean meats, lentils, fruits, and vegetables are excellent foods to eat to round out a protein shake diet.

Q:

Can I drink more protein shakes if I’m also working out, or is drinking more than the daily requirement of protein bad for health across the board?

A:

A person’s protein requirements will be based on their weight and activity levels. Therefore, the needs for someone who works out consistently will be higher than those for someone who is more sedentary.

However, a diet should be well balanced and include healthful fats and fibrous carbohydrates in addition to the right amount of protein based on needs. Consuming too much protein can have negative effects on health, however.

It is best to include a variety of whole foods in the diet over too many protein shakes.

Natalie Olsen, R.D., L.D., ACSM EP-C Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.