- What are protein shakes?
- Decreased appetite
- Healthy metabolism & lean muscle
- Weight loss
- Weight management
- Which type of protein is best?
- Dosage & side effects
Protein is an important nutrient for weight loss.
Getting enough protein can help support a healthy metabolism and reduce your appetite. It can also help you lose body fat without losing muscle.
Protein shakes are an easy way to add more protein to your diet, and they have been shown to help with weight loss.
This article explains everything you need to know about protein shakes and how they may affect your weight.
What are protein shakes?
Protein shakes are drinks made by mixing protein powder with water or another liquid, although other ingredients are often added as well.
They can be a convenient addition to your diet, especially when your access to quality high-protein foods is limited.
Although most people don’t need protein shakes to meet daily protein requirements, they can be useful if you need to increase your intake or have trouble meeting your needs through food alone.
You can buy protein powder and mix it yourself, or you can get many different brands of pre-made liquid shakes.
Some of the most popular types of protein powder on the market are:
- Whey protein: quickly absorbed, dairy-based, contains all the essential amino acids
- Casein protein: slowly absorbed, dairy-based, contains all essential amino acids
- Soy protein: plant-based, contains all essential amino acids, also contains soy isoflavones that may provide some health benefits
- Hemp protein: plant-based, contains all essential amino acids, rich in omega-3 and omega-6 fats, has a high arginine content
- Rice protein: plant-based, lower in the essential amino acid lysine
- Pea protein: plant-based, contains all essential amino acids, potentially is a less allergenic alternative than protein derived from soy or wheat
Certain protein powders and drinks contain a mix of different types of protein.
For example, many plant-based brands combine types to complement amino acid profiles. Some dairy-based protein powders combine whey and casein to provide both immediate and longer-lasting effects on muscle synthesis.
Summary: Protein shakes can contain different types of protein, each with its own nutrient profiles and possible benefits.
Protein shakes may decrease hunger and appetite
Protein has been shown to help decrease hunger and appetite.
One key reason for this is that protein generally helps you feel satisfied for longer than other macronutrients. This is due in part to the release of satiety hormones GLP-1 and PYY.
Studies also show that higher consumption of protein may result in less hunger throughout the day.
In one small 2005 study, a high-protein breakfast helped older female participants consume up to 135 fewer calories later in the day, compared with a low-protein breakfast or skipping breakfast.
In another small study from 2013, when older teen girls categorized as living with extra weight ate a higher-protein breakfast, they reportedly felt less hungry throughout the day than participants who ate no breakfast or a standard-protein breakfast.
A 2016 meta-analysis of five studies also found a connection between higher protein intake and increased fullness, although the authors cautioned that factors such as body weight, eating behavior, and other health issues all play a role in the sensations of fullness.
Only a small number of studies looked at protein shakes and appetite specifically, including one very limited study from 2019 conducted on nine young women with obesity. It found ingesting a whey protein drink actively reduced appetite.
Suggested read: Does too much whey protein cause side effects?
Another small study in men from 2011 found that drinking 20 grams of either casein and pea protein 30 minutes before a meal increased satiety and reduced the amount of food eaten, with a caveat that when the protein drinks were consumed right before the meal, this effect was not seen.
So while the evidence connecting protein shakes to weight loss or weight maintenance is promising, internal and external factors play a major role in how strong the connection may be.
Summary: Protein may decrease your appetite by affecting your hunger hormones. It may also help you feel full for longer.
Protein shakes can help maintain a healthy metabolism and lean muscle
A high-protein diet — especially when combined with strength training — can help you build muscle. And because muscle aids in metabolism and energy production (among other things), building muscle is a great way to keep your metabolism healthy.
This is especially true for individuals who are eating less due to a doctor-recommended weight loss plan.
Extreme calorie restriction can sometimes result in muscle loss in addition to fat loss. This loss of lean muscle can slow down your metabolism, which may make it easier to gain the weight back once you go off the restrictive diet.
Including sufficient protein intake and strength training while eating at a calorie deficit can help prevent this muscle loss and result in a metabolic slowdown.
A 2016 study investigated whether consuming extra protein per week (in the form of a shake) in combination with resistance training would improve outcomes of older adults with obesity during a 13-week weight loss program that included a calorie deficit. Participants given an extra 20 grams of protein weekly gained 2.8 lbs (1.3 kg) more muscle mass during their training program.
Suggested read: When is the best time to take protein?
In another 2016 study, researchers gave participants a combination of foods and shakes resulting in either a lower protein diet or a higher protein diet. After 6 weeks of following the diet (which included fewer calories for both groups), those on the higher-protein diet gained 2.4 lbs (1.1 kg) more muscle and lost 2.9 lbs (1.3 kg) more fat.
The thermic effect of protein may also provide a slight metabolism boost. Your body requires more energy to digest protein than it does fat or carbohydrates, which means more calories are burned in the process.
Summary: Protein may temporarily increase metabolism because of the energy required to digest and metabolize it. When combined with resistance training, adding more protein can also help you build muscle, especially if you’re eating less due to a doctor-approved diet.
Protein shakes may help you lose weight and belly fat
Researchers generally agree that high-protein diets can help you lose more fat, especially fat from the belly area.
In a smaller study from 2004, participants on a diet consisting of 25% of calories from protein lost 10% more belly fat after 12 months than those eating half that amount.
A larger study from 2009 found that when adults with obesity ate a diet higher in protein and lower on the glycemic index, their weight loss was better maintained than adults who didn’t. And a 2014 update to that study found those adults who continued to eat a diet higher in protein also continued to see improved weight loss maintenance.
Because there are so many lifestyle and ingredient variables involved in weight loss studies, it’s hard to draw a direct connection between drinking protein shakes and losing weight.
A small study from 2017 did find that when participants dealing with excess weight drank low sugar protein shakes as part of a “diet modification program,” their weight loss improved.
Summary: Protein shakes are a convenient way to increase your daily protein intake. When consumed as part of a reduced-calorie diet, protein shakes may support fat loss — especially from around your mid-section. However, many other variables also play a part.
Protein shakes may help with weight management
Protein’s effect on metabolism, appetite, and muscle mass may also keep you from regaining weight once you’ve successfully lost it.
Suggested read: The 7 best types of protein powder
A study from 2005 found that when participants who had lost weight from a specific diet program were given 30 grams of protein in addition to their regular diet during a “weight management” period of 6 months, they regained less weight than participants who didn’t have the supplemented protein.
A 2015 literature review suggests that higher protein intakes (1.2–1.6 grams per kg, or 25–30 grams of protein per meal) appear to improve both weight loss and weight management. Yet, researchers caution that full adherence to a higher-protein diet and other lifestyle factors are usually required for this improvement.
Summary: Additional protein, whether from shakes or whole foods, can help minimize the amount of weight you regain after weight loss.
Which type of protein is best?
Different types of protein may affect your body in distinct ways.
For instance, whey is absorbed quicker than casein. This makes it optimal for promoting muscle protein synthesis after exercise and could help you feel less hungry in the short term.
While some small studies have shown whey protein to be more effective than soy and other plant-based proteins when it comes to weight loss, other small studies show no real difference.
This seems to support the idea that individuals and their individual lifestyle factors are more important than the type of protein when it comes to weight loss or other desired outcomes.
One key factor to consider is the quality of the protein you purchase.
Whey, casein, and soy are considered “complete” proteins. This means they contain all the essential amino acids your body needs but may induce an allergic reaction in some people.
While rice and hemp proteins are often considered less allergenic options, they tend to be low in the essential amino acid lysine. Pea protein is also low in the amino acids cysteine and methionine.
As long as you are consuming a variety of protein sources throughout the day, these deficiencies likely won’t cause a problem. But it’s always a good idea to talk with your doctor or consult with a registered dietitian before incorporating any new supplements into your diet.
Summary: The exact type of protein powder you use for protein shakes shouldn’t make a major difference in fat loss, which means it’s more important to consider your individual health factors and dietary preferences.
Dosage and side effects of protein shakes
The Food and Drug Administration (FDA) doesn’t typically review supplements for safety and effectiveness before they hit the shelves, so it’s important to research any ingredients you might be ingesting, as well as the trustworthiness of the brand.
When possible, choose a protein that has been through the USP Dietary Supplement Verification Program.
Additionally, different brands of protein powder will often suggest different serving sizes. Make sure to check nutrition labels to find the right amount of supplemental protein for you.
If you’re lactose intolerant and drinking protein shakes made with whey or casein, you may experience side effects such as:
These symptoms can be avoided by switching to protein powders not derived from dairy, such as those made with protein from:
While most research suggests a high protein diet is safe for most individuals, it may be less safe for those living with underlying kidney issues. If you believe or know you have kidney complications, talk with your doctor before increasing your protein intake.
For reference, the recommended minimum amount of protein for an adult assigned male at birth under the age of 65 is around 56 grams per day. It’s around 67 grams per day for those older than 65.
For an adult assigned female at birth, the recommended minimum amount of protein is about 48 grams per day for those 65 and younger, and 57 grams per day for those over 65.
Summary: Third-party verification, nutrition labels, dietary preferences, and individual health factors should be considered when supplementing a diet with protein shakes.
Most adults can easily eat enough protein through food sources without using protein shakes.
Suggested read: Should you have a protein shake before or after your workout?
That said, protein shakes are an easy, safe, and often delicious way to add extra protein to your diet.
If you’re trying to lose weight or manage your weight, extra protein from shakes may help you feel less hungry, help you maintain muscle and metabolism, and lower the likelihood of regaining the lost fat, especially when combined with an exercise routine.