“High protein diet”, “eat 25g of protein with each meal”, “eat more protein” — sound familiar?

If not, where have you been? By now in your journey toward greater health and fitness, it’s almost impossible to have not heard of high protein diets — ones like the Atkins diet,” “Paleo”, or “the Zone.” You may have even tried one of those, or the seemingly endless variations.

And if you’ve spent any time looking into these diets, a lot of people claim to have had success losing weight with them — and their success is often attributed to their high protein nature.

But do these diet plans really work? Maybe these people just uncovered another “secret” along the way?

Or are they just marketing gimmicks?

Calories In, Calories Out — wait, there’s more?

Eating “high protein” is typically defined as getting 30% of your daily calories from protein. But before diving into whether high protein diets actually work for weight loss, you need to understand the bigger picture. Protein is just one part of a multi-faceted nutritional system: you and your macronutrient requirements.

What you eat can be broken down into 3 macronutrients: Proteins, Carbohydrates, and Fats. Unless you have a specific medical condition, you need all 3 to maintain proper health and functioning. Without sufficient amounts of any of these sources, your body will not operate at peak condition. And without a proper balance of these nutrients during a diet program will hinder the success you achieve in reaching your goals.

When trying to lose weight, you need to eat fewer calories from these nutrients than you expend. For example, if you determine that, between your Basal Metabolic Rate and your activity (from moving, eating, and exercising), you burn 2,000 calories per day, to stay the same weight you’d have to eat roughly 2,000 calories every day. However, to lose weight, you would have to place yourself into a caloric deficit. A caloric deficit indicates that you are eating less calories than you burn per day — i.e., in this case, potentially restricting intake to only 1,800 calories per day.

But as we already mentioned, though calories consumed versus calories burned ultimately determines success or failure in the weight game, is it all that matters?

Well, it depends.

If your goal is simply to lose weight, regardless of whether it be fat- or muscle-weight lost, then yes, calories are all that matter.

However, if you’re attempting to improve your body composition by losing Body Fat Mass and gaining Skeletal Muscle Mass, then no, calories are not all that matters. Balancing your macro nutrients properly does.

And that’s where protein comes in.

Protein Primer

So how does protein fit into the picture? Well, as mentioned above, protein is one of the 3 basic macronutrients you find in your food.

To break it down further, proteins are made up of smaller units called amino acids. There are 22 amino acids, however, 9 of these amino acids are called “essential” — meaning you need to eat them because the body can’t produce them on its own. You can get these essential amino acids by eating protein-rich foods like eggs, meat, and fish, as well as vegetarian/vegan options, like nuts, seeds, beans, and tofu. Generally, you cannot get all the essential amino acids from just one food item, so eating a variety of animal and plant-based proteins are recommended.

But that’s not all.

Besides being something you eat, protein has its fingers in just about every structure and function of your body. For example:

Antibodies: these proteins fight foreign “invaders” of your body, like in allergic reactions.

Repair, maintenance, and structure: proteins are the main building blocks of your muscles, bones, skin, and hair.

Hormones: chemical messenger proteins allow cells and organs to communicate. For example, Growth Hormone — which can affect your muscle gain and fat loss results — and Follicle Stimulating Hormone — a hormone important to your sexual health — are both protein hormones.

Enzymes: while all proteins are not enzymes, all enzymes are proteins — and proteins are catalysts (“kickstarters”) for chemical reactions in your body.

Transportation and storage: some proteins carry important molecules where they’re needed — think hemoglobin (red blood cells) carrying oxygen to cells, then carrying carbon dioxide away.

Clearly, protein serves many roles within the body. Therefore, not getting enough protein in your diet can have serious consequences-for your health. Without enough protein, your muscles may begin to atrophy (waste)– taking Lean Body Mass (LBM), strength, and energy with them.

Any injuries you suffer will take longer to heal, as well. This is because wound healing relies on good nutrition, and good nutrition includes adequate protein. A strong connection between protein deficiency and slow wound healing has been shown.

Finally, not eating enough protein impairs your immune system, placing you at a greater risk of infections while reducing your ability to fend off disease once it takes hold.

The Effects of High Protein in Your Diet

Now that you know everything you never wanted to know about protein’s roles in the body, take a look at a few of the positive effects of increasing your protein intake and how that can relate to your body composition goals.

Appetite

Eating more protein helps suppress hunger and appetite for longer than eating the same amounts of the other macros (fats and carbs). This means that eating 100 calories from protein will leave you more satiated than 100 calories from either carbohydrate or fatsources.

In a study of 12 healthy women, those that were fed a greater amount of protein (30% protein, 40% carbohydrate, 30% fat) had higher GLP-1 levels — a hormone that helps reduce appetite — for 24 hours after eating as compared to when they consumed a low protein diet (10% protein, 60% carbohydrate, 30% fat).

Coupled with other markers, like metabolic rate and thermogenesis (the heat caused by breaking down molecules of food), this indicated that the higher protein diet led to significantly reduced feelings of hunger.

Another, larger study of adults not only agreed with the findings of the previous study but added that participants eating the higher-protein diet spontaneously ate 400 fewer calories each day, despite having no restrictions on the rest of their diet.

The findings of both these studies suggest that protein causes a cascade of reactions in the human body that results in a reduced appetite and greater satiety — leading to fewer calories eaten over the course of the day and more easily-maintained dieting — which means an increased chance of weight-loss success.

Metabolic Rate

Eating more protein has also been shown to increase your Energy Expenditure — i.e., the number of calories you burn each day. Several studies found that people eating high protein diets ended up burning more calories for several hours after eating.

One such study took healthy young women and fed them either a high-protein or high-carbohydrate meal. 2.5 hours after eating, thermogenesis was doubled in those that ate the high-protein meal, versus those that ate the high-carbohydrate meal.

While this may be a temporary increase, all things equal, it results in more calories burned by the end of the day.

The findings of another study agreed that EE was increased with higher protein consumption — and it also showed that 42% of this increase in EE was due to gluconeogenesis — your body generating energy from non-carbohydrate (fat) stores.

So as an added bonus, not only does eating more protein improve your metabolism through thermogenesis — it also causes an increase in the number of calories burned from Fat Mass.

Body Composition

In addition to the points made above, eating higher amounts of protein can have positive effects on your body composition through more direct pathways. As alluded to earlier, protein is a far-spread component of your body. Consuming higher amounts helps protect your non-fat (read: muscle) body mass.

39 adults were split into 3 groups. While all groups were on a diet and fitness regimen, the first was fed the recommended Regular Daily Amount (RDA) of protein, set at 0.8 grams of protein per kilogram. The second and third groups were fed 2xRDA amounts (1.6g/kg) and 3xRDA amounts (2.4g/kg), respectively.

While you don’t necessarily need to eat protein in these drastic amounts to see benefits, those in this study eating the greater-than-RDA amounts of protein lost the most fat mass and maintained the most fat-free mass.  

Other, similar studies have shown this, including one that indicated a loss of 3.3 kilograms more fat lost in a high-protein-eating group compared to a high-carbohydrate-eating group.

Because eating higher protein spares more muscle mass, as you lose weight your total LBM remains higher, maintaining a larger, more efficient metabolism.

This was clearly shown in a study from 2013 that favored high-protein diets for bodyweight management and suggested that, while 0.8 grams of protein per kilogram of body weight is sufficient for weight management, 1.2g/kg preserved metabolism and lean mass considerably better.

Since a greater amount of Lean Body Mass means your metabolism is larger and EE increased — thus burning more calories — being able to keep a greater proportion of that lean mass is very desirable. These studies suggest that increasing your protein intake while reducing caloric intake helps you do that while dieting for weight loss.

The Verdict

On the surface, losing weight looks simple. But when you’re after improving not just the number on the scale, but the quality contained in that number, it becomes more complicated.  Since you’re trying to lose weight, you care about your appearance and health and probably don’t want to be “flabby” — so you need at least some muscle mass.

And to maintain your current muscle mass — or improve it — you need to eat enough protein. The studies above have proven that.  But you also need to eat fewer calories than you expend — and that’s not always easy.

The good news is, getting a higher percentage of your daily calories from protein can make all of that a little bit easier.

In this post you learned that your diet is composed of 3 primary macronutrients: proteins, fats, and carbohydrates — and that while losing weight can be as simple as eating fewer calories than you burn, this isn’t the most efficient way to better health.

Protein has a lot to do with your body’s structure, function, and health, and in conjunction, eating more of it can help you reduce your appetite, improve your metabolism, and change your body composition — which often includes losing weight.  

So ultimately, the answer to the question posed at the beginning of this article is a resounding yes.

Protein can help you lose weight, and it can help you do so while maintaining muscle mass, resulting in a leaner, more muscular body. This means you’re more likely to reach your goal, improve your health, and ultimately, improve your life.

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Matthew Seiltz is a writer and lifelong strength and fitness enthusiast. When not writing or working out, he can be found with a book or spending time with his wife and sons outdoors.