Protein is the single most important nutrient for weight loss and a better looking body.
A high protein intake boosts metabolism, reduces appetite and changes several weight-regulating hormones (1, 2, 3).
Protein can help you lose weight and belly fat, and it works via several different mechanisms.
This is a detailed review of the effects of protein on weight loss.
Protein Changes The Levels of Several Weight Regulating Hormones
Your weight is actively regulated by your brain, particularly an area called the hypothalamus (4).
In order for your brain to determine when and how much to eat, it processes multiple different types of information.
Some of the most important signals to the brain are hormones that change in response to feeding (5).
A higher protein intake actually increases levels of the satiety (appetite-reducing) hormones GLP-1, peptide YY and cholecystokinin, while reducing your levels of the hunger hormone ghrelin (6, 7, 8, 9, 10).
By replacing carbs and fat with protein, you reduce the hunger hormone and boost several satiety hormones.
This leads to a major reduction in hunger and is the main reason protein helps you lose weight. It can make you eat fewer calories automatically.
Protein reduces levels of the hunger hormone ghrelin, while it boosts the appetite-reducing hormones GLP-1, peptide YY and cholecystokinin. This leads to an automatic reduction in calorie intake.
Digesting and Metabolizing Protein Burns Calories
After you eat, some calories are used for the purpose of digesting and metabolizing the food.
This is often termed the thermic effect of food (TEF).
Although not all sources agree on the exact figures, it is clear that protein has a much higher thermic effect (20-30%) compared to carbs (5-10%) and fat (0-3%) (11).
If we go with a thermic effect of 30% for protein, this means that 100 calories of protein only end up as 70 usable calories.
About 20-30% of protein calories are burned while the body is digesting and metabolizing the protein.
Protein Makes You Burn More Calories (Increases “Calories Out”)
Due to the high thermic effect and several other factors, a high protein intake tends to boost metabolism.
It makes you burn more calories around the clock, including during sleep (12, 13).
A high protein intake has been shown to boost metabolism and increase the amount of calories burned by about 80 to 100 per day (14, 15, 16).
This effect is particularly pronounced during overfeeding, or while eating at a caloric surplus. In one study, overfeeding with a high protein diet increased calories burned by 260 per day (12).
By making you burn more calories, high protein diets have a “metabolic advantage” over diets that are lower in protein.
A high protein intake can make you burn 80-100 more calories per day, with one study showing an increase of 260 calories during overfeeding.
Protein Reduces Appetite and Makes You Eat Fewer Calories
Protein can reduce hunger and appetite via several different mechanisms (1).
This can lead to an automatic reduction in calorie intake.
In other words, you end up eating fewer calories without having to count calories or consciously control portions.
Numerous studies have shown that when people increase their protein intake, they start eating fewer calories.
This works on a meal-to-meal basis, as well as a sustained day-to-day reduction in calorie intake as long as protein intake is kept high (17, 18).
In one study, protein at 30% of calories caused people to automatically drop their calorie intake by 441 calories per day, which is a huge amount (19).
So, high protein diets not only have a metabolic advantage – they also have an “appetite advantage,” making it much easier to cut calories compared to lower protein diets.
High-protein diets are highly satiating, so they lead to reduced hunger and appetite compared to lower protein diets. This makes it much easier to restrict calories on a high-protein diet.
Protein Cuts Cravings and Reduces Desire for Late-Night Snacking
Cravings are the dieter’s worst enemy.
They are one of the biggest reasons why people tend to fail on their diets.
Another major problem is late-night snacking. Many people who have a tendency to gain weight get cravings at night, so they snack in the evening. These calories are added on top of all the calories they ate during the day.
Interestingly, protein can have a powerful effect on both cravings and the desire to snack at night.
This graph is from a study comparing a high-protein diet and a normal-protein diet in overweight men (20):
protein reduces cravings
The high-protein group is the blue bar, while the normal-protein group is the red bar.
In this study, protein at 25% of calories reduced cravings by 60% and cut the desire for late-night snacking by half!
Breakfast may be the most important meal to load up on the protein. In one study in teenage girls, a high-protein breakfast significantly reduced cravings (21).
Eating more protein can lead to major reductions in cravings and the desire to snack late at night. These changes should make it much easier to stick to a healthy diet.
Protein Makes You Lose Weight, Even Without Conscious Calorie Restriction
Protein works on both sides of the “calories in vs calories out” equation. It reduces calories in and boosts calories out.
For this reason, it is not surprising to see that high-protein diets lead to weight loss, even without intentionally restricting calories, portions, fat or carbs (22, 23, 24).
In one study of 19 overweight individuals, increasing protein intake to 30% of calories caused a massive drop in calorie intake (19):
In this study, the participants lost an average of 11 pounds over a period of 12 weeks. Keep in mind that they only added protein to their diet, they did not intentionally restrict anything.
Although the results aren’t always this dramatic, the majority of studies do show that high-protein diets lead to significant weight loss (25).
A higher protein intake is also associated with less belly fat, the harmful fat that builds up around the organs and causes disease (26, 27).
All that being said, losing weight is not the most important factor. It is keeping it off in the long-term that really counts.
Many people can go on “a diet” and lose weight, but most end up gaining the weight back (28).
Interestingly, a higher protein intake can also help prevent weight regain. In one study, a modest increase in protein intake (from 15 to 18% of calories) reduced weight regain after weight loss by 50% (29).
So not only can protein help you lose weight, it can also help you keep it off in the long-term (3).
Eating a high-protein diet can cause weight loss, even without calorie counting, portion control or carb restriction. A modest increase in protein intake can also help prevent weight regain.
Protein Helps Prevent Muscle Loss and Metabolic Slowdown
Weight loss doesn’t always equal fat loss.
When you lose weight, muscle mass tends to be reduced as well.
However, what you really want to lose is body fat, both subcutaneous fat (under the skin) and visceral fat (around organs).
Losing muscle is a side effect of weight loss that most people don’t want.
Another side effect of losing weight is that the metabolic rate tends to decrease.
In other words, you end up burning fewer calories than you did before you lost the weight.
This is often referred to as “starvation mode,” and can amount to several hundred fewer calories burned each day (30, 31).
Eating plenty of protein can reduce muscle loss, which should help keep your metabolic rate higher as you lose body fat (32, 33, 34, 35, 36).
Strength training is another major factor that can reduce muscle loss and metabolic slowdown when losing weight (37, 38, 39).
For this reason, a high protein intake and heavy strength training are two incredibly important components of an effective fat loss plan.
Not only do they help keep your metabolism high, they also make sure that what is underneath the fat actually looks good. Without protein and strength training, you may end up looking “skinny-fat” instead of fit and lean.
Eating plenty of protein can help prevent muscle loss when you lose weight. It can also help keep your metabolic rate high, especially when combined with heavy strength training.
How Much Protein is Optimal?
The DRI (Dietary Reference Intake) for protein is only 46 and 56 grams for the average woman and man, respectively.
This amount may be enough to prevent deficiency, but it is far from optimal if you are trying to lose weight (or gain muscle).
Most of the studies on protein and weight loss expressed protein intake as a percentage of calories.
According to these studies, aiming for protein at 30% of calories seems to be very effective for weight loss.
You can find the number of grams by multiplying your calorie intake by 0.075. For example, on a 2000 calorie diet you would eat 2000 * 0.075 = 150 grams of protein.
You can also aim for a certain number based on your weight. For example, aiming for 0.7-1 gram of protein per pound of lean mass is a common recommendation (1.5 – 2.2 grams per kilogram).
It is best to spread your protein intake throughout the day by eating protein with every meal.
Keep in mind that these numbers don’t need to be exact, anything in the range of 25-35% of calories should be effective.
More details in this article: How Much Protein Should You Eat Per Day?
In order to lose weight, aiming for 25-35% of calories as protein may be optimal. 30% of calories amounts to 150 grams of protein on a 2000 calorie diet.
How to Get More Protein in Your Diet
Increasing your protein intake is simple. Just eat more of protein-rich foods.
Meats: Chicken, turkey, lean beef, pork, etc.
Fish: Salmon, sardines, haddock, trout, etc.
Eggs: All types.
Dairy: Milk, cheese, yogurt, etc.
Legumes: Kidney beans, chickpeas, lentils, etc.
You can find a long list of healthy high-protein foods in this article.
If you’re eating low-carb, then you can choose fattier cuts of meat. If you’re not on a low-carb diet then try to emphasize lean meats as much as possible. This makes it easier to keep protein high without getting too many calories.
Taking a protein supplement can also be a good idea if you struggle to reach your protein goals. Whey protein powder has been shown to have numerous benefits, including increased weight loss (40, 41).
Even though eating more protein is simple when you think about it, actually integrating this into your life and nutrition plan can be difficult.
I recommend that you use a calorie/nutrition tracker in the beginning. Weigh and measure everything you eat in order to make sure that you are hitting your protein targets.
You don’t need to do this forever, but it is very important in the beginning until you get a good idea of what a high-protein diet looks like.
There are many high-protein foods you can eat to boost your protein intake. It is recommended to use a nutrition tracker in the beginning to make sure that you are getting enough.
Protein is The Easiest, Simplest and Most Delicious Way to Lose Weight
When it comes to fat loss and a better looking body, protein is the king of nutrients.
You don’t need to restrict anything to benefit from a higher protein intake. It is all about adding to your diet.
This is particularly appealing because most high-protein foods also taste really good. Eating more of them is easy and satisfying.
A high-protein diet can also be an effective obesity prevention strategy, not something that you just use temporarily to lose fat.
By permanently increasing your protein intake, you tip the “calories in vs calories out” balance in your favor.
Over months, years or decades, the difference in your waistline could be huge.
However, keep in mind that calories still count. Protein can reduce hunger and boost metabolism, but you won’t lose weight if you don’t eat fewer calories than you burn.
It is definitely possible to overeat and negate the calorie deficit caused by the higher protein intake, especially if you eat a lot of junk food.
For this reason, you should still base your diet mostly on whole, single ingredient foods.
Although this article focused only on weight loss, protein also has numerous other benefits for health.