Written by Mary Jane Brown, PhD, RD (UK) on December 10, 2017
When it comes to weight loss, a high-protein diet can have powerful and beneficial effects.
With many options for boosting protein intake, it can be difficult to determine the best type of protein for weight loss.
This article reviews different types of protein and how they affect weight loss.
For example, overweight adults lost an average of 11 pounds (5 kg) over 12 weeks when they increased their protein intake from 15% to 30% of daily calories, without changing any other part of their diet (6).
A high protein intake may help you maintain weight loss, as well. One study found that a slightly higher intake of protein (18% of daily calories compared to 15%) resulted in a 50% lower body weight regain (9).
There are a number of reasons why high-protein diets boost weight loss:
- Keep you fuller for longer: Protein is highly satiating, meaning you stay fuller for longer. This can lead to an automatic reduction in calorie intake (6, 7).
- Reduce cravings: A high-protein diet has been linked to reduced cravings and a lower desire to snack at night (2).
- Increase calorie burn: Increased protein intake has been shown to have a higher thermic effect. This means it can boost the number of calories burned by up to 80 to 100 per day (10, 11, 12, 13).
- Change weight hormones: Protein has been shown to reduce levels of the hunger hormone ghrelin and boost the appetite-reducing hormones GLP-1 and PYY (14, 15, 16).
There are various protein sources, which makes it easy to follow a high-protein diet.
Generally, these sources are divided into two types: natural protein from foods or supplemental protein, usually in the form of protein shakes.
Summary High-protein diets lead to weight loss and may also help prevent weight regain. They do so by reducing hunger hormones, increasing satiety, burning more calories and decreasing cravings.
Certain foods are naturally very high in protein, and regularly eating these foods has been linked to weight loss.
One study found that overweight adults lost a similar amount of weight when they followed either a weight loss diet rich in plant proteins or a weight loss diet rich in animal proteins (24).
Other studies found similar results. Diets high in plant-based protein had benefits for weight loss, appetite control and food intake similar to those of diets high in animal-based protein (25, 26, 29).
- Eggs: 6 grams of protein in 1 large egg
- Nuts: 6 grams of protein in 1 ounce (28 grams) of almonds
- Chicken: 53 grams of protein in 1 chicken breast, cooked
- Cottage cheese: 23 grams of protein in 1 cup (210 grams)
- Cheese: 7 grams of protein in 1 ounce (28 grams) of cheddar cheese
- Greek yogurt: 17 grams of protein in 6 ounces (170 grams)
- Milk: 8 grams of protein in 1 cup
- Lean beef: 22 grams of protein in 3 ounces (85 grams)
- Fish: 39 grams in 1 cup (154 grams) of tuna
- Quinoa: 8 grams of protein in 1 cup (185 grams), cooked
- Lentils: 18 grams of protein in 1 cup (198 grams), cooked
Summary Boost your protein intake by including a variety of high-protein foods in your diet. Both plant- and animal-based protein sources are great for promoting weight loss.
Whey is a milk-based protein. It contains all the essential amino acids and is absorbed quickly in the body (31).
When overweight and obese adults took 56 grams of whey protein daily for 23 weeks, they lost 5 pounds (2.3 kg) without changing anything else in their diet (34).
These benefits are likely due to whey protein’s effects on satiety. A number of studies have found that whey protein may be superior at reducing feelings of hunger compared to other types of protein, such as casein, tuna, turkey and egg albumin (37, 38).
For example, one study among male athletes found that consuming whey protein shakes immediately decreased hunger by 50–65% (39).
This may be because whey protein is more quickly absorbed than other protein supplements, such as casein, and is effective at preventing hunger short-term (31).
However, the evidence is mixed. Some studies report that despite improved satiety, there may be no difference in fat loss or food intake compared to supplementing with other types of protein, such as soy, rice or egg protein (31, 40, 41).
Summary Whey protein is linked to weight loss, increased satiety and improved body composition. It may be superior in its effect on satiety compared to other protein sources.
Similar to whey protein, casein is milk-based and contains all the essential amino acids. However, it is absorbed slowly in the body (31).
Casein has also been linked to improved body composition and increased feelings of fullness.
Among male athletes, taking 70 grams of casein in the morning and evening over 8 weeks increased lean muscle mass by an average of 2.4 pounds (1.1 kg) (42).
Compared to whey protein, casein does not seem to be as effective at increasing muscle mass. However, it does appear more effective than other protein supplement sources, such as soy and wheat protein (43, 44, 45, 46).
When it comes to satiety, whey protein is absorbed quickly and can enhance feelings of fullness. Casein is digested more slowly and may keep you fuller over a longer period of time (29).
One study followed overweight men on a weight loss diet that included either whey or casein supplements. After 12 weeks, those taking casein supplements lost an average of 8% of their body weight. Those taking whey lost an average of 4% (47).
However, this study was small and the evidence is mixed.
Other studies comparing the effects of casein and whey found no significant difference in weight loss or body composition in the long-term, making them equally as good for weight loss (48).
Summary Casein is absorbed slowly, so may be more satiating in the long-term. Taking it regularly has been linked to weight loss and improved body composition.
Soy protein is plant-based, as it is made from soybeans. Unlike many other plant-based proteins, it contains all the essential amino acids.
In addition, it contains soy isoflavones, which are naturally occurring antioxidants that may have other health benefits.
When it comes to weight loss and soy protein, the scientific evidence is mixed.
Some studies suggest that soy protein can boost weight loss. For example, postmenopausal women who regularly took soy isoflavone supplements experienced greater weight loss than those who didn’t take supplements (49).
Another study among obese diabetic patients found that a weight loss diet including soy-based meal replacements like shakes resulted in an average of 4.4 pounds (2 kg) greater weight loss compared to a standard weight-loss diet (50).
What’s more, one study found that soy supplements may be just as effective as other protein sources for weight loss (40).
When obese adults were put on a weight-loss diet supplemented with either soy protein or whey and egg protein, both groups lost a similar amount of weight — an average of 17.2 pounds (7.8 kg) over 12 weeks.
However, a recent review of over 40 studies looked at the effects of soy protein on weight, waist circumference and fat mass and found no real benefits of soy supplements (51).
Only in very specific circumstances were soy and soy isoflavones associated with a lower BMI, such as in women taking doses less than 100 mg per day and over 2–6 month periods.
Summary Soy protein supplements may have benefits for weight loss. However, the evidence is weak and some studies show no real benefits for weight loss.
Rice protein is a plant-based protein. It is considered an incomplete protein due to its low levels of the essential amino acid lysine.
It is often mixed with pea protein to create a more complete and favorable amino acid profile.
There are currently very few studies on rice protein.
However, one study among young males found that 8 weeks of supplementing with whey or rice protein resulted in reduced fat mass and an increase in lean muscle mass, with no differences between the protein sources (41).
Nevertheless, more research is needed to determine the role of rice protein in weight loss.
Summary Limited evidence suggests that rice protein may improve body composition like whey protein. However, more research is needed.
Pea protein powder is a relatively new plant-based protein made from yellow split peas. It is commonly considered a complete protein source, as it contains all the essential amino acids.
Pea protein has also been linked to increased feelings of fullness.
One study in rats found that pea protein was absorbed slower than whey protein but faster than casein. Additionally, it was as good at boosting satiety levels as the dairy proteins (52).
Another study among 32 men found that consuming 20 grams of pea protein 30 minutes before a meal led to increased satiety and reduced calorie intake later in the day (53).
However, timing may be important. When the same participants consumed the pea protein immediately before the meal, it had little impact on food intake.
In addition to increased satiety, pea protein may have beneficial effects on body composition.
In one study, men who consumed 50 grams of pea protein daily for 12 weeks experienced similar increases in lean muscle mass as those taking the same amount of whey protein (54).
Although the initial research on pea protein is promising, more high-quality studies are needed to confirm any benefits for weight loss.
Summary Pea protein has been associated with increased satiety, reduced calorie intake and improved muscle mass. However, more high-quality studies are needed.
Although lacking scientific evidence, there are several other protein sources believed to have benefits for weight loss.
- Hemp protein: This is another plant-based protein that is high in healthy omega-3 and omega-6 fatty acids and fiber. However, it is low in the essential amino acids lysine and leucine, so it isn’t considered a complete protein source (55).
- Bone broth protein:Bone broth protein is made by boiling the bones of animals to release nutrients. It is not a complete protein, as it is missing some branched-chain amino acids. However, it does contain many other valuable nutrients.
- Egg protein powder: Egg protein is typically made from egg whites and is a complete protein. It can contain extra vitamins and is low in fat and carbs. Early studies suggest egg protein has little effect on appetite or weight (53, 56).
Summary Hemp protein, bone broth protein and egg protein powder are often promoted as beneficial for weight loss. However, there are not enough scientific studies available to back these claims.
When it comes to weight loss, it is very important to increase your protein intake. Where the protein comes from seems to be less important.
The scientific evidence is strongest in support of natural protein from foods, as well as whey and casein protein supplements for weight loss.
A protein intake between 0.5–1 gram per pound of body weight (1.2–2.2 grams/kg) daily, or 25–35% of total daily calories, seems most beneficial for weight loss.
Increasing your protein intake by eating more whole foods is best. Whole foods contain other nutrients and aren’t as processed as protein supplements.
However, protein powders can be convenient when time is short. They may also be beneficial for people who struggle to meet their protein needs via food, such as athletes, vegans or vegetarians and the elderly.
If your goal is weight loss, protein supplements should not be taken on top of your usual diet but rather as a replacement for other calories.
To get started following a high-protein diet for weight loss, read this article next.
Source: Health Line