Lean protein is the darling of the diet industry. Still married to the same low-fat dogma that brought us the obesity epidemic in the first place, mainstream weight-loss programs can’t recommend a diet based on fat. With the growing popularity of low-carb diets for weight loss, carbohydrates have also become a black sheep, leaving protein as the only “good” macronutrient left.
Paleo dieters, fortunately, aren’t interested in conforming to mainstream nutritional guidelines. Healthy animal fats are the backbone of a Paleo eating plan: even the much-demonized saturated fat is nothing to be afraid of. But this doesn’t mean that a Paleo diet excludes the other macronutrients – carbohydrates are a hotly debated topic, but everyone agrees that a healthy diet includes at least some protein. The question is not whether to eat protein, but how much protein is ideal for optimum health.
What Is Protein?
Biologically speaking, proteins are complex molecules (polymers) formed from smaller subunits called amino acids. Each of the 20 known amino acids amino acid belongs to one of three groups. The first group, called the essential amino acids, includes the ten amino acids that your body cannot make on its own; you have to get enough of them in your diet. In the second group, the nonessential amino acids, are all the amino acids that you can synthesize either from essential amino acids or from protein. Despite their name, these amino acids aren't any less important than their essential cousins. They might not be “essential” to get in the diet, but they’re still “essential” from your body’s point of view. The third group, the conditional amino acids, contains the amino acids that are usually nonessential, but become essential when your body is under stress (for example, if you get sick).
Protein plays many important roles in the body. It’s a fundamental building block, functioning as the structural “skeleton” for cells. Various types of proteins also perform an enormous number of functions – enzymes (the substances that drive biochemical reactions like digestion) are a type of protein, other proteins help cells in your body communicate, and special motor proteins are responsible for large-scale movements like muscle contraction as well as the microscopic movements involved in cell reproduction. Proteins also help transport substances within the body, and can combine to form even more sophisticated mechanisms.
Making sure to get all 10 essential amino acids every day sounds like a tedious chore, but fortunately the answer is very simple: eat meat. Almost any kind of animal product (meat, eggs, or dairy) is a “complete protein,” meaning it contains all the essential amino acids, so on a Paleo diet, getting your amino acids in shouldn’t be a problem. The only people who have to worry about mixing and matching specific protein sources are vegetarians, since plant proteins like beans are generally not complete.
Goldilocks and the Macronutrient Ratios: How Much is Just Right?
Protein indisputably plays an important part in almost every physical process, and unlike glucose (which your body can synthesize if you aren’t eating carbohydrates), you can’t manufacture protein from other sources. If you don’t eat enough essential amino acids, your body will start breaking your muscles down to get them. In other words, any healthy diet needs adequate protein, preferably the complete proteins found in animal products.
At the lower limit, a diet consisting of 10% protein by caloric intake will meet your essential needs. Eating less than 10% protein for an extended period of time risks deficiencies in one or more essential amino acids. On a Paleo diet, eating less than 10% protein is also quite difficult – you’d have to make a serious effort to restrict your meat intake and choose only the fattiest cuts.
10% could thus be considered the lower end of the healthy range of protein consumption. At the other end of the spectrum, a “high-protein diet” contains 20-29% protein, while a “very high protein diet” is 30-39% protein. The human body’s ability to metabolize protein ends at around 35%. Thus “high protein” is a relative term: even advocates of higher protein consumption are not claiming that it should account for the majority of calories.
Note that these ratios are based on a fairly normal (approximately 2,000-calorie) diet. The absolute amount of protein is also significant. At the very upper limit, protein toxicity begins to set in when you eat more than 230 grams (920 calories) of protein a day (remember that this is not the same as eating 920 calories of meat, since some of the calories in meat come from fat). On a 2,000 calorie diet, 920 calories is 46% of energy from protein, well above even the “very high protein” range. On a 5,000 calorie diet, however, a toxic level of 920 calories is only 18% of energy. This means that on a very high calorie diet, the percentage of protein must be lower to stay within a healthy range.
These calculations leave us with a fairly wide range of potential protein consumption – 10% to 35% of the diet, as long as protein does not comprise more than 920 calories total. A human could survive on any protein intake within this range, but that does not mean that the optimal protein intake is so broad. Traditional hunter-gatherer diets offer a clue as to how much protein the human body is equipped to handle. Loren Cordain estimates that hunter-gatherers traditionally ate around 19-35% of energy as protein, but this is probably an overestimation because Cordain bases his calculations on the “average” animal when in fact, hunter-gatherers wisely singled out the fattest animals in the herd for consumption. Most hunter-gatherers probably consumed closer to 10-20% of calories from protein. Thus, for people with no special nutritional considerations, 10-20% protein is a reasonable starting point.
The Dangers of Excess Protein
Consistently eating inadequate protein (less than 10%) will cause serious problems, but in the real world it doesn’t happen often. Especially on a Paleo diet, most people have very few problems eating enough protein. A more common problem is eating too much. A relatively high protein diet (20-29% protein) might not be ideal, but it probably won’t do any serious damage, especially if you eat that protein along with high-quality fat and carbohydrates. Some people, however, fall into the trap of trying to get much larger percentages of total energy from protein, especially after drastically cutting their carbohydrate consumption when they stop eating grains.
In many cases, this overconsumption of protein is simply due to a lingering fear of fat –restricting carbohydrates is not completely alien to mainstream diet advice, but if you were raised to think that “low-fat” was synonymous with “good for you,” learning to embrace butter as a health food can be a challenge. Many people stumble at first by trying to eat a “low-fat Paleo” diet, which automatically ends up being high-protein, because if you restrict carbohydrates and fat, protein is the only energy source left. This kind of diet could easily contain 60-70% of calories as protein – a meal of skinless chicken breast or tuna with vegetables doesn’t offer much in the way of fat or carbs.
At first, this diet can make maintaining a caloric deficit fairly painless: since protein is the most satiating macronutrient, eating a lot of protein helps you stop feeling hungry quickly. This sating effect, however, doesn't last forever – in the short term, a high-protein diet can help you feel full while in a caloric deficit, but in the long run, your body will adjust. On the other hand, such an extreme excess of protein can quickly lead to a whole range of health problems.
Protein toxicity is a general term that refers to the harmful effects of eating too much protein. It is caused both by the absolute amount of protein in your diet, and by the ratio of protein to the other macronutrients (carbohydrates and fat). When you break down protein into energy, the kidneys first need to remove nitrogen from the amino acids, a process called deamination. This process produces a chemical called ammonia as a byproduct. Since ammonia is highly toxic, your liver converts it into a waste product called urea, which passes out of the body through urine. Eating too much protein can thus put unnecessary stress on your liver and kidneys, as they struggle to convert the protein into a useful form of energy.
Processing ammonia properly also requires carbohydrates and fat as co-factors, so an overload of protein without the other two macronutrients is doubly stressful. This is why lean protein is so satiating – your body recognizes that it can only digest a relatively small amount, so you feel full quickly. Fatty meats are comparatively less satiating because your body has enough co-factors (fat) to process more of the protein.
If you only eat protein without any accompanying fat or carbs, not only will you overwork your liver and kidneys, but you also won’t get enough of the fat-soluble micronutrients that your body needs for other important processes. The health problems that result from this kind of extreme protein overload are well documented. The Inuit referred to protein toxicity as “rabbit starvation,” not because it results from eating too much “rabbit food” in the form of raw vegetables, but because the Inuit suffered from it when the only food they could obtain was rabbit, which is a very lean meat. The symptoms of “rabbit starvation” are weakness, weight loss, and a general feeling of illness. Excess protein consumption can also lead to mood problems and anxiety, by interfering with the proper function of neurotransmitters in the brain.
While dietary protein overload can cause serious problems, periodic protein restriction – much like intermittent fasting – can actually be very beneficial. Intermittent protein restriction helps your cells perform a kind of “spring cleaning” of old and useless proteins that would otherwise accumulate in your body. This process is called autophagy; it’s also one of the benefits of intermittent fasting, but for this particular perk, you don’t necessarily have to abstain from all food. Restricting protein alone (while eating as much fat and as many carbohydrates as you feel hungry for) will provide the same result.
Protein for Athletes
Weightlifters and bodybuilders are often extremely skeptical of any advice to restrict protein – conventional wisdom dictates that to gain muscle, you need to eat extremely high levels of protein all the time, digging into piles of tuna and chicken breasts, and chugging down protein shakes after every meal. Muscle is indeed built of protein, but protein consumption won’t necessarily cause muscle gain any more than fat consumption will cause fat gain. For most people attempting to gain muscle, it’s primarily important to have a calorie surplus. If you eat more calories than you burn, you will gain weight. If you train correctly, that weight will be muscle. You could theoretically eat a calorie surplus of lean protein, but you could also eat the same number of calories from fat and achieve the same results without the drawbacks of a high-protein diet.
The exceptions to this are people who train at an extremely competitive level and want to gain muscle beyond the normal range of the human body. This is the level of athletics where eating for performance begins to differ from eating for health. Powerlifters or professional bodybuilders do need to eat more protein, especially if their diet is also relatively low in carbohydrates. All the drawbacks of a high-protein diet still apply; these athletes have simply decided that the trade-off (increased muscle mass) is worth it. For most people, however, the primary goal of exercise is health rather than competition, so consuming extreme amounts of protein would be counterproductive.
Thus, while athletes might want to stay in the upper end of the 10-20% range, and highly competitive strength athletes probably need even more than that, most people should have no need to go overboard. Protein powders, in particular, are one of your worst options: not only are they usually unnecessary, but they present protein in isolation (without any carbs or fat to help you metabolize it), after it’s been heavily processed and loaded with all kinds of artificial colors and flavorings. If you need a quick and portable post workout meal, try some hard-boiled eggs or leftover meat with a baked sweet potato.
Practical Takeaway: Protein for a Paleo Diet
Claiming that a certain percent of the diet should be protein is scientifically very interesting, but this kind of recommendation is not directly applicable to the way most of us think about food. People don’t buy “36 grams of protein;” they buy half a dozen eggs, or a nice piece of salmon. Weighing and measuring everything you eat is always an option, but this can be irritatingly time-consuming and often impractical. Fortunately, it isn’t necessary. Most of us can make a rough visual estimate of how much food we’re hungry for; learning to do the same for protein isn’t difficult.
The table below shows the recommended daily protein consumption for several different groups of people. In general, eating around 0.7 grams of protein per pound of total mass, or 1 gram per pound of lean mass, will put you within a healthy range of approximately 15% protein (assuming a normal caloric intake – people on a very high-calorie or very low-calorie diet will have different needs). Since your protein needs will vary depending on your lean body mass, women (who naturally have a higher body fat percentage) will have lower protein requirements per pound of total weight than men. The table shows several general recommendations; body fat percentage is within the normal range for all age/sex groups.
The meal plans aren’t designed to be rigid templates, or even nutritionally complete (they only include the protein-containing foods at every meal). Rather, they can give you an idea of what “100 grams of protein” looks like on your plate, to help you make real-life food choices that adequately meet your protein needs.
| Person | Protein Needs | Meal Plan 1 (3 meals) | Meal Plan 2 (2 meals) |
| Child (age 9-10) 65 lbs total weight 17% body fat 54 lbs lean mass | 46-54 grams | Breakfast: 2-egg omelet with veggies (12g) Lunch: salmon arugula salad (3oz of salmon) (24g) Dinner: stuffed pork tenderloin (2oz of pork) (14g) Total: 50g protein | Meal 1: portobello burger (85% lean beef; 5oz patty) (35g) Meal 2: chicken thighs and vegetables (1 thigh) (16g) Total: 51g protein |
| Teenage boy 120 lbs total 12% body fat 106 lbs lean mass | 84-106 grams | Breakfast: 4-egg omelet with veggies (24g) Lunch: salmon arugula salad (4oz of salmon) (32g) Dinner: stuffed pork tenderloin (5oz of pork) (35g) Total: 91g protein | Meal 1: portobello burger (85% lean beef; 8oz patty) (56g) Meal 2: chicken thighs and vegetables (2 thighs) (32g) Total: 88g protein |
| Teenage girl 105 lbs total 20% body fat 84 lbs lean mass | 74-84 grams | Breakfast: 3-egg omelet with veggies (18g) Lunch: salmon arugula salad (4oz of salmon) (32g) Dinner: stuffed pork tenderloin (4oz of pork) (28g) Total: 78g protein | Meal 1: portobello burger (85% lean beef; 8oz patty) (56g) Meal 2: chicken thighs and vegetables (1.5 thighs) (24g) Total: 80g |
| Adult man 180 lbs total 15% body fat 153 lbs lean mass | 126-153 grams | Breakfast: 4-egg omelet with veggies (24g) Lunch: salmon arugula salad (8oz of salmon) (64g) Dinner: stuffed pork tenderloin (6oz of pork) (42g) Total: 130g protein | Meal 1: portobello burger (85% lean beef; 10oz patty) (70g); 2 deviled eggs (12g) Meal 2: chicken thighs and vegetables (3 thighs) (48g) Total: 130g protein |
| Adult woman 125 lbs total 20% body fat 100 lbs lean mass | 88-100 grams | Breakfast: 4-egg omelet with veggies (24g) Lunch: salmon arugula salad (5oz of salmon) (40g) Dinner: stuffed pork tenderloin (5oz of pork) (35g) Total: 99g protein | Meal 1: portobello burger (85% lean beef; 8oz patty) (56g) Meal 2: chicken thighs and vegetables (2 thighs) (32g) Total: 88g protein |
In general, to stay within an adequate range of protein consumption, just focus on fat as your main source of calories (but not necessarily the main part of your diet by volume). Don’t eat protein without fat – choose fatty cuts of meat like pork shoulder and lamb, and eat your chicken with the skin on. There’s nothing wrong with lean meats like tuna, but make sure to eat them accompanied by some other fat source, like this delicious tuna steak with avocados.
Conclusion
Protein is an essential macronutrient that supports almost every type of cell in your body. While it’s important to get enough high-quality animal protein, humans were never designed to use it as our main energy source. If you’re new to Paleo, it’s especially important to remember that fat, not protein, should make up the bulk of your calories: there’s no such thing as “low-fat Paleo.” All the calculations about percentages and grams per pound of body weight can be fascinating, but if they seem overwhelming, there’s no need to spend time and energy worrying about them. Simply eating a variety of fatty meats as part of a well-balanced diet should keep most people within a healthy range of protein consumption without needing to pull out the calculator.
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