Protein is an incredible essential macronutrient.

Fat is plentiful, even when you’re lean, and there are only two absolutely essential fatty acids; the rest we can manufacture from other precursors if required.

Carbs we can produce from protein, if we really must, or we can just switch over to ketones and fats for the bulk of the energy that would otherwise come from carbs.

Protein cannot be made with the raw material available in our bodies. We have to eat foods containing the range of amino acids that we need.

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In other words, protein is especially important—which is why today I'm writing a definitive guide on the subject. After today's post, you'll have a good handle on the role protein plays in the body, how much protein you need to be eating, which foods are highest in protein, and much more.

Platter of meats on a picnic table with family in background.

Gimme the Basics: Why Is Protein Important?

First, what roles does protein play in our bodies?

It helps us build muscle. We use it to construct new cells, muscles, organs, and other tissues.
It's a chemical messenger, allowing us to turn on and turn off genes.
It forms the fundamental substrates used to manufacture enzymes, DNA, and hormones.
It can even be a fuel source, either directly or through conversion into glucose.

Now, am I saying that the steak you eat directly becomes a thyroid hormone? Does chicken breast turn into DNA? No. But the strings of amino acids and peptides that make up proteins are eventually broken down and cobbled back together to fulfill all the roles I describe.

Every bite of protein you consume contributes toward maintenance of your physiology. And we can't make new protein. We have to eat it.

What's the Recommended Daily Protein Intake?

If you go by the official numbers, the Recommended Daily Intake (RDI) for protein is 0.8 grams of protein per kilogram of bodyweight, or 0.36 g protein/lb. That's what the "experts" say to eat. That's all you "need."

I disagree, and I'll tell you why down below, but there's the official answer. Sufficient is one thing. Optimal is another. In reality, the amount of protein required for optimal health and performance is different for every population.

Protein Intake for Athletes and Exercisers

Athletes need more protein than the average person, but perhaps not as much as most fitness enthusiasts think (or consume).

A 2011 paper on optimal protein intakes for athletes concluded that 1.8 g protein/kg bodyweight (or 0.8 g protein/lb bodyweight) maximizes muscle protein synthesis (while higher amounts are good for dieting athletes interested in preserving lean mass), whereas another settled on “a diet with 12-15% of its energy as protein,” assuming “total energy intake is sufficient to cover the high expenditures caused by daily training” (which could be quite high).^1,2
One study even found benefit in 2-3 g protein/kg bodyweight (0.9-1.4 g protein/lb bodyweight) for athletes, a significant increase over standard recommendations.³

That said, I wouldn’t be too quick to discount anecdotal evidence or “iron lore.” A significant-enough portion of the strength training community swears by 1-2 g protein/lb bodyweight that it couldn’t hurt to try if lower amounts aren’t working for you.

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Protein Intake During Weight Loss

Weight loss involves a caloric deficit (whether arrived at spontaneously or consciously). Unfortunately, caloric deficits rarely discriminate between lean mass and body fat, while most people are interested in losing fat, not muscle/bone/tendon/sinew/organ. Numerous studies show that increasing your protein intake during weight loss will partially offset the lean mass loss that tends to occur.

In obese and pre-obese women, a 750 calorie diet with 30% of calories from protein (about 56 grams) preserved more lean mass during weight loss than an 18% protein diet.⁴ Another study in women showed that a 1.6 g protein/kg bodyweight (or 0.7 g protein/lb bodyweight) diet led to more weight loss, more fat loss, and less lean mass loss than a 0.8 g protein/kg bodyweight diet.⁵
Among dieting athletes, 2.3 g protein/kg bodyweight (or a little over 1 g protein/lb bodyweight) was far superior to 1.0 g protein/kg bodyweight in preserving lean mass.
And, although specific protein intake recommendations were not stated, a recent meta-analysis concluded that high-protein weight loss diets help preserve lean mass.⁶

Protein Intake When Injured

Healing wounds increases protein requirements. After all, you’re literally rebuilding lost or damaged tissue, the very definition of an anabolic state, and you need protein to build new tissue. One review recommends around 1.5 g protein/kg bodyweight or close to 0.7 g protein/lb bodyweight for injured patients.⁷ Children recovering from illness or injury may need up to 2.5 g protein/kg. If you mess this up and undershoot your protein intake during recovery, you will compromise your healing.

Protein Intake for Seniors

The protein metabolism of the average senior citizen is compromised. They need more protein to do the same amount of "work." The protein RDA is simply not enough for seniors, who lose thigh muscle mass and exhibit lower urinary nitrogen excretion when given the standard 0.8 g protein/kg bodyweight.⁸

What’s good for the goose may not be good for the elderly, frail gander. For example, a baseline intake of 1.0-1.3 g protein/kg bodyweight or 0.5-0.6 g protein/lb bodyweight might be more suitable for the healthy and frail elderly to ensure nitrogen balance.⁹

That said, active seniors will do better with even more and evidence suggests that increasing protein can both improve physical performance without necessarily increasing muscle mass and increase muscle mass when paired with extended resistance training in the elderly.^10,11

How Much Protein on Keto?

What about another population entirely: ketogenic dieters. We've got a lot of those around here, so this is important. If you're on a keto diet, should you restrict protein? I mean, doesn't extra protein just convert directly into glucose?

Our livers only convert protein into glucose when we—for whatever reason—need more glucose. It's demand, not the supply.

And since keto-adapted people are running mostly on fat and ketones, they have a lower requirement for glucose and are much less likely to trigger the kind of perceived glucose deficiency that necessitates gluconeogenesis.

Extra protein can however impair ketogenesis by contributing oxaloacetate donors to the Krebs cycle. With oxaloacetate, fatty acids enter the Krebs cycle and are fully oxidized and turned into ATP, the body's energy currency. Without oxaloacetate, fatty acids can't enter the Krebs cycle and are instead converted into ketones to generate energy.

If you’re dealing with cognitive decline, elevated inflammation, or any other condition that requires or may improve with deep ketosis, aim for a lower protein content (10-15% of calories). Get those high ketone levels, see how it feels, and see if that’s the protein intake for you. Start low, really revel in those high ketone readings, and stick with them if you're improving.
If you’re losing weight (or trying to), eat closer to 15-30%. For you, the ketone readings aren’t the biggest focus. How you look, feel, and perform are your main concern. Eating slightly more protein will increase satiety, making “eating less” a spontaneous, inadvertent thing that just happens. It will also stave off at least some portion of the lean mass accretion that occurs during weight loss; you want to lose body fat, not muscle.
If you’re trying to gain large amounts of muscle, eat closer to 20-30%.

Understand, however, that everyone is unique. For some, protein is deeply anti-ketogenic—eating too much protein will knock you out of ketosis almost immediately. For others, protein has little to no effect. Or if it has a momentary nullifying effect, you can quickly slip back into ketosis. Unless deep ketosis is medically necessary, don't worry about protein too much either way. There are studies of "modified ketogenic diets" where protein goes as high as 30% of calories and subjects still get the benefits.¹²

High Protein Benefits

Beyond supporting the basic underpinnings of human physiology, eating more protein than the RDI offers extra benefits.

Protein Satiety

As a fundamental biological motivator, hunger can't be ignored forever. Eventually you crack, and the diet fails. Eventually, you're going to eat. Where extra protein helps is adding satiety. Successful fat loss comes down to managing your hunger; protein helps you manage it without relying on sheer willpower.

Protein For Muscle Gain and Muscle Retention

To increase muscle protein synthesis, you need two primary inputs: resistance training and protein intake.

You can lift all the weights in the world, but if you're not eating enough protein, you won't gain any muscle.

You can't make extra, it has to come from outside sources. And then during active weight loss, upping your protein intake will minimize the loss of muscle that usually accompanies fat loss. In women, for example, cutting calories while keeping protein higher than normal led to better lean mass retention than cutting the same number of calories and keeping protein low.¹³

Simply put, more protein tends to enhance fat loss and preserve muscle.

Protein to Increase Energy Expenditure

Metabolizing protein is costlier than metabolizing fat and carbohydrates: it takes extra energy to process protein than it does to process the other macronutrients. This increases the amount of calories you expend, simply by eating more protein. Thus, higher protein diets increase energy expenditure relative to diets lower in protein.

Higher Micronutrient Intake

While we love our fat-soluble vitamins around here—your vitamin Ds, your vitamin K2s, your retinols, your vitamin Es—we musn't forget about our B-vitamins and minerals. Those latter two groups come bound in the muscle meat. The more whole food-based protein we eat, the more micronutrients we'll take in.

Protein Foods: Where to Get Your Protein

The best sources of protein for humans are animal foods. Meat, fish, fowl, shellfish, eggs, and dairy all contain the most bioavailable form of protein: animal protein. Makes sense when you consider that we are animals, and we use the protein we eat to build new animal tissues in our own animal bodies. Of course animal protein will be better and more efficient at doing protein-y things than plant protein.

Following resistance training, soy protein blunts testosterone production in men.¹⁴
In both the young and the elderly, whey promotes greater muscle protein synthesis than soy protein.¹⁵
Compared to milk, soy protein results in less hypertrophy following resistance training.¹⁶
Women who consume animal protein have greater muscle mass than female vegetarians.¹⁷

We can also confirm this by studying the Biological Value (BV) of a given protein source. The BV describes the proportion of protein in a food that becomes incorporated into the consuming organism's tissues, with 100 being best.

Egg protein: 100 BV
Whey isolate: 100 BV
Milk protein: 91 BV
Beef: 80 BV
Casein: 77 BV

And then:

Soy protein: 74 BV
Wheat gluten: 64 BV
Pea protein: 65 BV

Another factor to consider is that animal protein is complete; it contains all the essential amino acids—those amino acids which we cannot produce ourselves and must obtain from outside sources. Plant proteins tend to be incomplete. No individual plant protein is complete, except for perhaps potato protein (but the absolute levels of protein in a potato are too low).

If you want to go all plant, you have to combine different ones to hit all the amino acids you need. So in theory you could get your protein from an algorithmically-derived blend of gluten powder, pea protein, rice protein, and fermented free range soy. Or you could just eat 5 eggs for breakfast (30 grams), a Big Ass Salad with a can of oysters (11 grams), some cheese (8 grams), and a can of sardines (24 grams) on top for lunch, and a ribeye for dinner (40-80 grams, depending on size). I know what I'd choose. I know what's easier, what's more delicious.

Collagen Protein

Collagen protein is the type of protein you get from connective tissue in meats. You can slow-cook tougher cuts of meat until they're tender, or simmer a batch of bone broth to get your collagen. Collagen is so important that I consider it the fourth macronutrient. It contains amino acids that aren't as plentiful in muscle meats and other protein sources, so it helps your body complete the amino acid chains that would otherwise be limited. You get more benefit out of the other protein you eat by eating collagen-rich foods or supplementing with a hydrolyzed collagen protein supplement.

How about you, folks? How do you get your protein? How much do you eat per day?

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* This blog reflects my personal views and opinions and isn’t intended as medical advice, but I hope it will be informative and inspiring as you pursue a healthy, fulfilling life.

The Definitive Guide to Protein