“How much protein should I eat?” is usually the first question someone asks once they start hitting the gym and hoisting some iron. If the person you’re asking knows what they’re talking about, you probably won’t get a straightforward answer. A handful of variables come into play when determining optimal protein intake for building muscle and cutting body fat.
Old-school bodybuilding dogma preaches that athletes and gym-goers should eat copious amounts of protein to build muscle, but is there any scientific evidence to substantiate that claim?
Well, the topic of protein requirements for athletes and active individuals remains controversial and open to interpretation.
A research review back in 2000 contends that the protein requirements of active individuals may be twice those of sedentary people. Even so, the author notes that most active people only require 0.6-0.8 g protein/lb body weight, which is quite similar to what more recent studies suggest.
However, the review concludes that “protein requirements” are likely below what is necessary to optimize athletic performance.
Asking “How much protein do I need a day?” isn’t necessarily synonymous with “How much protein should I eat?”
Protein is an essential macronutrient for humans, meaning we need to consume it regularly for proper health and longevity.
The current recommended daily allowance (RDA) for protein is 0.8 g/kg body weight, or a mere 0.36 g/lb body weight. Any bodybuilder would (understandably) scoff at that recommendation. The dietary need for protein is quite low compared to the amount of protein you should eat for optimal muscle growth and fat loss.
It’s essential to differentiate between the RDA for protein and “optimal protein intake for active people” since the RDA is a guideline for general public health, not for athletic performance and building muscle.
The RDA for protein is the amount the average adult should consume for proper health and biological function. For athletes, bodybuilders, etc., the amount of protein you should eat a day depends on several factors, notably lean body mass, age, type of training you engage in, and activity level.
Thankfully, there are quite a few studies that discuss protein needs for building muscle and burning body fat.
A formative systematic review by Helms et. al contends that strength-training athletes and bodybuilders may benefit from daily protein intakes in the range of 1.0-1.4 g/lb lean body mass (LBM), especially when trying to lean out and cut body fat.
Note that LBM is what you weigh, not including body fat.
Lean Body Mass Example: a 200-lb person with 10% body fat has 180 lbs of LBM. A 250-lb person with 30% body fat has 175 lbs of LBM.
But why use lean body mass instead of total body weight?
It’s simple. If the two individuals in the above example use their total body weight to calculate optimal protein intake, the obese 250-lb person will consume significantly more protein despite having less lean body mass.
It’s more sensible to base your protein needs off lean body mass instead of total body weight since excess fat tissue (i.e., white adipose tissue) is not metabolically demanding. People who are obese/overweight will overestimate their actual protein needs if they use total body weight as the starting parameter.
Arguably the most pervasive myth about high-protein diets is that they are harmful and unhealthy.
Well, no. Just no.
The myth that high-protein diets are harmful stems from the fact that the kidneys filter nitrogenous waste (which comes predominantly from amino acids in protein). While that is true, high-protein diets are not harmful to the kidneys in healthy individuals. They can, however, be dangerous if you have preexisting renal issues because your body won’t be able to properly eliminate urea, ammonia, creatinine, and other nitrogenous byproducts.
An article published in Nutrition & Metabolism concludes:
“Protein restriction may be appropriate for treating existing kidney disease, but we find no significant evidence for a detrimental effect of high protein intakes on kidney function in healthy persons after centuries of a high-protein Western diet.”
Moreover, several long-term studies show no adverse health effects from high-protein diets (3-4 times the RDA). Research even suggests that high-protein intake has a favorable impact on body composition, fat loss, waist circumference, blood glucose balance, and appetite regulation.
Now, does this mean you should gorge on protein if you have healthy kidneys?
Certainly not. Like anything else you put in your body, there are caveats to consuming excessive amounts of protein. Depending on which protein sources you consume, a high-protein diet may increase the acid load to the kidneys.
It’s imperative to eat plenty of alkaline-forming foods, such as potassium-rich fruits and vegetables, to maintain a proper acid-base balance in the body on a high-protein diet. You should also consider incorporating more non-animal protein sources, like seafood, rice protein, and pea protein. These are generally lower in saturated fat and less acidic than red meat, eggs, and dairy.
Health and fitness subculture has a propensity to create false dichotomies, leading athletes, bodybuilders, and gym-goers alike down one of two extreme paths. It looks like protein recommendations have succumbed to this phenomenon.
According to “hardcore” bodybuilding magazines, you need a whopping 2+ g protein/lb body weight per day, whereas the RDA for protein is a lowly 0.36 g protein/lb body weight. Notice how polarizing those “suggestions” are?
Sure, 2+ g protein/lb body weight might make sense if you’re taking every performance-enhancing drug under the sun, while the RDA is reasonable if you have no intention of touching a barbell anytime soon.
But for most active individuals and athletes, the answer to "How much protein should I eat?" lies near the middle of the extremes.
Based on the research mentioned earlier, active individuals who regularly train with weights should consume between 0.8-1.4 g protein/lb LBM per day to build muscle, assuming you’re eating a sufficient amount of total calories.
A low-protein diet (e.g. 0.5-0.6 g protein/lb LBM) is not ideal for building muscle, but neither is a super-high-protein diet (e.g. 2+ g protein/lb LBM). Many bodybuilders and sports nutritionists will argue that there are no “negatives” to overfeeding on protein since the excess is less likely to contribute to body fat gain.
Theoretically, it makes perfect sense that overfeeding on protein generally has no negative impact on body composition.
In fact, multiple longitudinal crossover studies show that resistance trainees consuming an additional 450-800 calories per day from protein did not gain body fat or weight. Though, the subjects in these studies were undergoing intense resistance training and had variable intakes of other macronutrients.
A few plausible explanations for the findings of those studies:
Protein (per gram) has the highest net thermic effect of feeding (TEF). Your body expends more energy to digest and assimilate protein than it does carbohydrates and fats.
Protein is highly satiating. Hence, eating a high-protein diet helps control food intake and energy balance, which is ultimately the most critical factor for building muscle and losing weight.
Excess protein isn’t preferentially converted to triglycerides (i.e., it’s less likely to be stored as body fat)
The short answer: Yes. The amino acids in protein can be converted to fatty acids.
Lipogenesis (the creation of new fats) is an energy-consuming process, meaning you need to be in a positive calorie/energy balance for it to take place. The central molecule that feeds into lipogenesis is acetyl-CoA.
Image courtesy of the Royal Society of Chemistry
During an energetic surplus, the carbon skeletons of amino acids can be converted to acetyl-CoA, ultimately leading to fat synthesis (lipogenesis). However, amino acids are the body’s last resort for acetyl-CoA and energy (ATP) since glucose and dietary fats are much more “potent” in ATP potential per molecule.
Assuming you’re eating a fairly balanced diet (i.e., not a fad diet), the contribution of amino acids to ATP synthesis and fatty acid synthesis is marginal compared to glucose and dietary fat. Glucose and fatty acids are the body’s preferred substrates for both ATP and lipogenesis.
A theoretical, but likely inconsequential, “backdoor” route for fatty acid synthesis could occur through specific glucogenic amino acids (e.g., glutamine, alanine, leucine). Glucogenic amino acids are substrates for gluconeogenesis - the process by which the body creates glucose from non-sugar molecules.
While superficially plausible, gluconeogenesis is not a significant source of glucose in a positive energy balance unless your diet is wildly imbalanced. Several studies report excess protein does not significantly increase blood glucose.
One study had subjects consume a massive 136 g of protein from 3 lbs of beef, which the researchers estimate could yield 68 g of glucose through gluconeogenesis. Yet, they found no increase in blood glucose in the eight hours after feeding.
It’s not entirely clear what the fate of excess protein is, but the data indicates it doesn’t contribute much to lipogenesis.
Many gym newbies assume that eating more protein = more muscle growth.
Sure, eating more than 1.4 g protein/lb LBM won’t be detrimental to muscle growth, but it won’t necessarily be better. People have this notion that excess protein leads to “extra” muscle growth, which is simply not the case.
Overfeeding on protein may be counterproductive for bodybuilders and athletes who want to build muscle. If anything, it will increase satiety and the thermic effect of feeding, preventing you from getting the calories you need to grow.
There is an intrinsic “cap” to muscle protein synthesis in response to high-protein meals. After MPS reaches its peak, a refractory period of roughly four hours sets in before skeletal muscle is “resensitized” to the anabolic effects of amino acids. Research scientists refer to this phenomenon as the “muscle-full effect.”
At any given meal, 20-40 g of a leucine-rich protein source (e.g., whey protein, dairy protein, animal protein, eggs) will elicit peak muscle protein synthesis in most individuals. Intuitively, larger, muscular people require more protein to maximize MPS, and vice versa. The “extra” protein from a meal will be subject to fecal excretion, use for other biological functions (e.g., neurotransmitter and enzyme synthesis), gluconeogenesis, or oxidation for energy.
Research also tells us that insulin amplifies the muscle protein synthetic response to a high-protein meal, and carbohydrates are protein-sparing molecules. Thus, athletes and bodybuilders are better off eating enough protein in conjunction with plenty of carbs (e.g., 30+ grams) to maximize muscle protein synthesis at every feeding.
The muscle-full effect gives us insight into why an intermittent fasting diet might be suboptimal for building muscle. You can’t starve yourself all day and then play “catch up” at night by overfeeding protein in a short time frame. While you certainly can build muscle doing intermittent fasting, it’s likely not ideal for maximizing muscle growth.
Protein is essential for preserving lean body mass when calorie intake is low. The last thing you want to do is skimp on protein when your main goal is to lose weight.
Assuming you hit the gym regularly and lift weights four or more times per week, a good starting point for protein intake is 1.0 g/lb LBM, if not higher. Some people may benefit from protein intake between 1.5-1.7 g/lb LBM if they are on a very-low-calorie diet, such as in the final weeks of a bodybuilding contest prep or when trying to cut weight for a weigh-in.
Recall from earlier that high-protein diets increase the thermic effect of feeding (TEF) - the amount of energy the body expends to digest and absorb nutrients. High-protein diets can also reduce the intake of other macronutrients by promoting satiety.
Therefore, a high-protein diet makes perfect sense when your goal is to cut body fat and lose weight.
Moreover, very-low-carb diets aren’t inherently optimal for fat loss since carbohydrates are protein-sparing molecules and have an additive effect on muscle protein synthesis. Consuming a modest amount of carbohydrates with a complete protein source will augment the MPS response to each meal, thereby helping you preserve more muscle tissue while cutting body fat.
Eating quality sources of protein is crucial for optimizing muscle growth while bulking up and preserving muscle on a fat-loss diet.
Naturally, you might be wondering what makes a certain protein source "high quality"? In short, quality sources of protein provide high amounts of essential amino acids (EAAs), especially branched-chain amino acids (BCAAs) like L-leucine.
Why is L-leucine so important, you ask?
Research makes it evident that muscle protein synthesis is commensurate with L-leucine content in a protein source. In other words, a food source that provides 500-1,000 mg L-leucine per 20 g of protein will elicit a significantly lower MPS response in comparison to an equal amount of protein that contains 3,000-4,000 mg of L-leucine.
Furthermore, protein sources that lack a sufficient amount of any one of the nine EAAs will lead to suboptimal MPS. Thankfully, there are many “complete” protein sources out there. You can also “mix and match” incomplete protein sources in a complementary fashion to create a complete protein, such as rice protein and pea protein in Organic Vegan protein powder.
The best protein sources in terms of their completeness and biological value include:
Mixing up your protein sources adds a nice variety to your diet without sacrificing optimal muscle protein synthesis. Just be sure you focus on both quality and quantity when it comes to protein sources.
The logical response to “How much protein should I eat?” is “It depends.” There is no all-encompassing optimal protein intake, or diet, for that matter.
To get you out of the gate, try using these starting guidelines to protein intake for building muscle and losing weight:
- For building lean muscle, aim for roughly 1 gram of protein per pound of lean body mass.
- For weight loss and cutting body fat, aim for 1.2-1.4 grams of protein per pound of lean body mass.
- Around 0.8-1.2 grams of protein per pound of lean body mass is adequate protein intake for most athletes who regularly lift weights.
- Sedentary adults generally only require the RDA for protein - 0.36 g/lb body weight.
- Older people may benefit from eating a little more protein to combat age-related sarcopenia.
- Consume at least 20-30 grams of leucine-rich protein per meal.
- Space protein-rich meals about 4-5 hours apart throughout the day.
- For building and maintaining lean muscle tissue, consume plenty of carbohydrates along with quality protein to optimize muscle protein synthesis and spare muscle tissue.
- Drinking a casein protein shake before bedtime will provide a sustained-release of amino acids while you sleep.
Remember, factors such as lean body mass, sex, age, genetics, and training experience will contribute to your unique protein demands. You will inevitably need to adapt and adjust throughout the process of dialing in your protein intake and learning more about which protein sources work best for you.
If you’re unsure how to determine your calorie and macronutrient needs appropriately, this nifty Calorie and Macro Calculator will do the trick!