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As with most things in nutrition, there’s no simple answer. Your ideal intake of calories and protein depends on your health, body composition, main goal, and the type, intensity, duration, and frequency of your physical activity. And even taking all this into account, you’ll end up with a starting number, which you’ll need to adjust through self-experimentation.
Your height, weight, age, and level of physical activity all contribute to your caloric needs. There are many calorie calculators out there, but the NIH Body Weight Planner stands out. It has been tested and validated against real-world data and can estimate the number of calories you need to reach then maintain a specific weight.
Calorie-wise, there are only three types of diets:
A hypocaloric diet feeds you fewer calories than you burn. If you want to lose weight, that’s the diet for you. If you want most of your weight loss to be in the form of fat, not muscle, you’ll also need to get enough protein and preferably to exercise.
A hypercaloric diet feeds you more calories than you burn. If you want to gain weight, that’s the diet for you. If you want most of your weight gain to be in the form of muscle, not fat, you’ll need to get enough protein and engage in resistance training (by lifting weights, for instance).
A eucaloric diet feeds you as many calories as you burn. It is also called a maintenance diet, since your weight won’t change much; but you can gain or lose fat or muscle, depending on how much protein and exercise you get.
Daily protein requirements are expressed in grams, either per kilogram of body weight (g/kg) or per pound of body weight (g/lb). Ranges in the table below reflect known individual variances.
If you’re sedentary, aim for 1.2–1.8 g/kg (0.54–0.82 g/lb). Keep in mind that your body composition will improve more if you add regular activity, especially resistance training, than if you merely hit a protein target.
If you’re of healthy weight, active, and wish to keep your weight, aim for 1.4–2.0 g/kg (0.64–0.91 g/lb). People who are trying to keep the same weight but improve their body composition (more muscle, less fat) may benefit from the higher end of the range.
If you’re of healthy weight, active, and wish to build muscle, aim for 1.8–2.4 g/kg (0.82–1.10 g/lb). If you’re an experienced lifter and bulking, intakes of up to 3.3 g/kg (1.50 g/lb) may help you minimize fat gain.
If you’re of healthy weight, active, and wish to lose fat, aim for 1.8–2.7 g/kg (0.82–1.23 g/lb), skewing toward the higher end of this range as you become leaner or if you increase your caloric deficit (by eating less or exercising more).
If you’re overweight or obese, aim for 1.2–1.5 g/kg (0.54–0.68 g/lb). This range, like all the others in this list, is based on your total body weight (most studies on people who are overweight or obese report their findings based on total body weight, but you’ll find some calculators that determine your optimal protein intake based on your lean mass or your ideal body weight).
If you’re pregnant, aim for 1.7–1.8 g/kg (0.77–0.82 g/lb).
If you’re lactating, aim for at least 1.5 g/kg (0.68 g/lb).
If you’re vegan or obtain most of your protein from plants, then your protein requirements may be higher because plant-based proteins are usually inferior to animal-based proteins with regard to both bioavailability and amino acid profile.
Also, note that …
Protein intake should be based on body weight, not on caloric intake. (But caloric intake should be based on body weight, too, so the two intakes are linked.)
Most studies have looked at dosages up to 1.5 g/kg; only a few have looked at dosages as high as 2.2–3.3 g/kg. However, in healthy people, even those higher dosages don’t seem to have negative effects.
How much protein you need depends on several factors, such as your weight, your goal (weight maintenance, muscle gain, or fat loss), your being physically active or not, and whether you’re pregnant or not.
You can quickly and easily calculate your optimal daily intake with our protein intake calculator.
For adults, the US Recommended Dietary Allowance (RDA) for protein is 0.8 g/kg. However, a more appropriate statistical analysis of the data used to establish the RDA suggests this number should be higher: 1.0 g/kg.
Note that, contrary to popular belief, the RDA doesn’t represent an ideal intake. Instead, it represents the minimum intake needed to prevent malnutrition. Unfortunately, the RDA for protein was determined from nitrogen balance studies, which require that people eat experimental diets for weeks before measurements are taken. This provides ample time for the body to adapt to low protein intakes by down-regulating processes that are not necessary for survival but are necessary for optimal health, such as protein turnover and immune function.
An alternative method for determining protein requirements, called the Indicator Amino Acid Oxidation (IAAO) technique, overcomes many of the shortcomings of nitrogen balance studies. Notably, it allows for the assessment of protein requirements within 24 hours, thereby not leaving the body enough time to adapt. Studies using the IAAO method have suggested that about 1.2 g/kg is a more appropriate RDA for healthy young men, older men, and older women.
Further evidence that the current RDA for protein is not sufficient comes from a randomized controlled trial that confined healthy, sedentary adults to a metabolic ward for eight weeks. The participants were randomized into three groups:
|Macronutrients||Low protein||Normal protein||High protein|
|Protein (% of caloric intake)|
|Fat (% of caloric intake)|
|Carbohydrate (% of caloric intake)|
Each diet was equally hypercaloric: each participant consumed 40% more calories than they needed to maintain their weight. Yet, as shown in the figure below, eating near the RDA for protein resulted in loss of lean mass, and while this loss is so small as to be nonsignificant, the higher protein intakes were associated with increases in lean mass.
Another takeaway from this study is that eating more than 1.8 g/kg doesn’t seem to meaningfully benefit body composition, which makes it a good higher end for your daily protein intake, provided that you aren’t physically active or trying to lose weight.
|Body weight (lb)||Body weight (kg)||Lower end (g)||Higher end (g)|
The RDA for protein (0.8 g/kg) underestimates the needs of healthy, sedentary adults, who should rather aim for 1.2–1.8 g/kg (0.54–0.82 g/lb).
If you’re physically active regularly, you need more protein daily than if you were sedentary. The American College of Sports Medicine, the Academy of Nutrition and Dietetics, and the Dietitians of Canada recommend 1.2–2.0 g/kg to optimize recovery from training and to promote the growth and maintenance of lean mass when caloric intake is sufficient. This recommendation is similar to that of the International Society of Sports Nutrition (ISSN): 1.4–2.0 g/kg.
Importantly, it may be better to aim for the higher end of the above ranges. According to the most comprehensive meta-analysis to date on the effects of protein supplementation on muscle mass and strength, the average amount of protein required to maximize lean mass is about 1.6 g/kg, and some people need upwards of 2.2 g/kg. Those of you interested in a comprehensive breakdown of this study will find one in NERD #34 (August 2017).
However, only 4 of the 49 included studies were conducted in people with resistance training experience (the other 45 were in newbies). IAAO studies in athletes found different numbers: on training days, female athletes required 1.4–1.7 g/kg; the day following a regular training session, male endurance athletes required 2.1–2.7 g/kg; two days after their last resistance-training session, amateur male bodybuilders required 1.7–2.2 g/kg.
Since higher protein intakes seem to have no negative effects in healthy people, one may want to err toward the higher amounts. For most athletes (and similarly active adults), the ISSN range (1.4–2.0 g/kg) will work well:
|Body weight (lb)||Body weight (kg)||Lower end (g)||Higher end (g)|
Athletes and similarly active adults can optimize body composition, performance, and recovery with a daily protein intake of 1.4–2.0 g/kg (0.64–0.91 g/lb) and a preference toward the upper end of this range.
Assuming progressive resistance overload and a mildly hypercaloric diet (370–800 kcal above maintenance), a few studies suggest you’ll gain less fat if you eat more protein (3.3 g/kg rather than 1.8–2.4 g/kg), although one did not.
What’s important to understand is that a daily protein intake of 3.3 g/kg isn’t likely to help you build more muscle than a daily protein intake of 1.8–2.4 g/kg. What the higher number can do is help you minimize the fat gains you’ll most likely experience if you eat above maintenance in order to gain (muscle) weight.
|Body weight (lb)||Body weight (kg)||Lower end (g)||Higher end (g)|
Hypercaloric diet. Intakes as high as 3.3 g/kg may help experienced lifters minimize fat gain while bulking.
Athletes and active adults can optimize muscle gain with a daily protein intake of 1.8–2.4 g/kg (0.82–1.10 g/lb). For experienced lifters on a bulk, up to 3.3 g/kg (1.50 g/lb) may help minimize fat gain.
First, let it be clear that, though it is possible to lose fat on a eucaloric diet (aka maintenance diet — a diet that provides as many calories as you burn) by shifting your macronutrient ratios toward more protein, if you want to keep losing weight you’ll need to switch to a hypocaloric diet (i.e., you’ll need to start eating fewer calories than you burn).
High protein intakes help preserve lean mass in dieters, especially lean dieters. An early review concluded that, to optimize body composition, dieting athletes (i.e., athletes on a hypocaloric diet) should consume 1.8–2.7 g/kg. Later studies have argued that, to minimize lean-mass loss, dieting lean resistance-trained athletes should consume 2.3–3.1 g/kg (closer to the higher end of the range as leanness and caloric deficit increase). This latter recommendation has been upheld by the International Society of Sports Nutrition and by a review article on bodybuilding contest preparation.
|Body weight (lb)||Body weight (kg)||Lower end (g)||Higher end (g)|
Hypocaloric diet. Intakes as high as 3.1 g/kg may enhance fat loss and minimize muscle loss in lean lifters.
Note that those recommendations are for people who are relatively lean already and trying to lose a little more fat while preserving their precious muscle mass. Several meta-analyses involving people with overweightness or obesity suggest that 1.2–1.5 g/kg is an appropriate daily protein intake range to maximize fat loss. This range is supported by the European Association for the Study of Obesity, which recommends up to 1.5 g/kg for elderly adults with obesity. It is important to realize that this range is based on actual body weight, not on lean mass or ideal body weight.
Dieting athletes benefit from higher protein intakes, relative to their weights, than overweight and obese dieters. This can be partly explained in three interrelated ways:
Overweight and obese individuals have sluggish metabolisms that tend to favor fat storage over protein storage (protein being stored as muscle). They usually need a greater caloric deficit to lose fat than do athletes (this rule isn’t absolute, since the closer an athlete gets to essential body fat, the harder it gets to lose fat).
Protein intake is based on total weight. Let’s consider two dieters who weigh the same. If one is an already lean athlete and the other an overweight individual, the latter will get to consume a lot fewer calories. Let’s say I’m an athlete consuming 3,000 kcal and 180 grams of protein (720 kcal): my diet is 24% protein. Now let’s say I’m overweight and consuming 2,000 kcal and 120 grams of protein (480 kcal): my diet is also 24% protein.
If an already lean athlete and an overweight person weigh the same, the former has more muscle and so needs more protein to maintain muscle mass.
Considering the health risks associated with overweightness and obesity, it is also noteworthy that eating a diet higher in protein (27% vs. 18% of calories) significantly reduces several cardiometabolic risk factors, including waist circumference, blood pressure, and triglycerides, while also increasing satiety. These effects are small, however, and likely dependent on the amount of body fat one loses.
|Body weight (lb)||Body weight (kg)||Lower end (g)||Higher end (g)|
Hypocaloric diet. If you’re overweight or obese, fat loss should be your priority, but that doesn’t mean you cannot build some muscle over the same period.
When dieting for fat loss, athletes and other active adults who are already lean may maximize fat loss and muscle retention with a daily protein intake of 2.3–3.1 g/kg (1.00–1.41 g/lb). People who are overweight or obese are best served by consuming 1.2–1.5 g/kg (0.54–0.68 g/lb).
Sarcopenia is a muscle disorder. It is defined as an impairment of physical function (walking speed or grip strength) combined with a loss of muscle mass. It is the primary age-related cause of frailty.
Frailty is associated with a higher risk of disabilities that affect your ability to perform daily activities, a higher risk of having to go to a nursing home, and a higher risk of experiencing falls, fractures, and hospitalizations.
The link between sarcopenia, frailty, and associated morbidities may explain why sarcopenia is associated with a greater risk of premature death and reduced quality of life. This isn’t a rare issue, either: in the US, over 40% of men and nearly 60% of women over the age of 50 have sarcopenia, and more than 10% of people in their 20s.
Reference: Janssen et al. J Am Geriatr Soc. 2002.
Fortunately, sarcopenia is neither inevitable nor irreversible — some seniors have built more muscle in their old age than they ever had in their youth. The older you get, though, the greater your muscles’ anabolic resistance (i.e., their resistance to growth), and so the greater the protein intake and exercise volume (of resistance training, preferably) you’ll need to stimulate muscle protein synthesis.
The protein RDA for adults over 50 is currently the same as for younger adults: 0.8 g/kg. Same as for younger adults, however, studies using the IAAO method have suggested that 1.2 g/kg would be a more appropriate RDA. Moreover, since a low protein intake is associated with frailty and worse physical function than a higher protein intake, several authorities now recommend that older adults consume 1.2–1.5 g/kg. Finally, while all adults have similar daily protein requirements, older adults have higher per-meal requirements.
Notably, doubling protein intake from 0.8 to 1.6 g/kg has been shown to significantly increase lean body mass in elderly men. Similar observations have been made in elderly women who increase their protein intake from 0.9 to 1.4 g/kg. Even a small increase in protein intake from 1.0 to 1.3 g/kg has minor benefits towards lean mass and overall body composition.
So how much protein should you get?
Sedentary but healthy seniors: 1.0–1.2 g/kg (0.45–0.54 g/lb)
Sick or injured seniors: 1.2–1.5 g/kg (0.54–0.68 g/lb)
Seniors wishing to lose weight: 1.5–2.2 g/kg (0.68–1.00 g/lb)
Seniors wishing to build muscle: 1.7–2.0 g/kg (0.77–0.91 g/lb)
Depending on their health statuses and goals, older adults (50+ years) should aim for a daily protein intake of 1.0–2.2 g/kg (0.45–1.00 g/lb).
The protein RDA for pregnant women is 1.1 g/kg. This value was estimated by adding three values:
The RDA for a healthy adult (0.8 g/kg)
The amount of additional body protein a pregnant woman accumulates
The amount of protein used by the developing fetus
However, as we saw previously with non-pregnant healthy adults, the RDA may not be sufficient, let alone optimal. There’s some IAAO evidence that the RDA for pregnant women should be about 1.66 g/kg during early gestation (weeks 11–20) and 1.77 g/kg during late gestation (weeks 32–38). Moreover, a meta-analysis of 16 intervention studies reported that protein supplementation during pregnancy led to reduced risks for the baby:
34% lower risk of low gestational weight
32% lower risk of low birth weight
38% lower risk of stillbirth
This effect was more pronounced in undernourished women than in adequately nourished women. Importantly, these values were determined from sedentary women carrying one child, meaning that pregnant women who engage in regular physical activity or are supporting the growth of more than one child may need even higher amounts.
Also, keep in mind that we can only tell you what the studies reported; we can’t possibly know about your health and your pregnancy specifically. Please be sure to consult with your obstetrician/gynecologist (ob/gyn) before making any changes.
|Body weight (lb)||Body weight (kg)||Weeks 11–20 (g)||Weeks 32–38 (g)|
Pregnant women may require a daily protein intake of at least 1.77 g/kg (0.8 g/lb) to support both the fetus and themselves. Protein supplementation during pregnancy appears to lower some risks for the baby — including the risk of stillbirth — especially in undernourished women.
As with pregnancy, there is little research investigating how lactation and breastfeeding affect protein requirements. Women produce a wide range of breast milk volumes, regardless of their energy status (i.e., milk production is maintained even among underweight women — i.e., women with a BMI under 18.5). The infant’s demands appear to be the primary regulator of milk production.
Based simply on adult protein requirements plus the protein output in breast milk, the RDA for lactating women was set at 1.3 g/kg. However, one study reported that half of the lactating women consuming 1.5 g/kg were in negative nitrogen balance, while another study suggested that 1.0–1.5 g/kg leads to a rapid downregulation of protein turnover suggestive of an adaptive response to insufficient intake.
Considering (1) the lack of data on the effects of a protein intake greater than 1.5 g/kg in lactating women and (2) that consuming 1.5 g/kg or less leads to adaptations suggestive of insufficient intake, lactating women should aim to consume at least 1.5 g/kg of protein daily.
|Body weight (lb)||Body weight (kg)||Protein intake (g)|
Lactating women should aim for a daily protein intake of at least 1.5 g/kg.
Breast milk is considered the optimal source of nutrition for infants (0–12 months old) and is recommended as the exclusive source of nutrition for infants aged 0–6 months. Based on the average weight and milk intake of healthy infants aged 0–6 months, their adequate protein intake is 1.5 g/kg.
The average protein intake for healthy infants aged 7–12 months is estimated at 1.6 g/kg, assuming that half their protein comes from breast milk and half from complementary foods. Yet the RDA is set at 1.2 g/kg for this age group based entirely on studies conducted in toddlers and children.
Although breast milk is considered the ideal food for infants, not all infants can breastfeed. Infant formulas provide an alternative, but there are considerable differences in composition from breast milk. One such difference is the protein content, which tends to be higher in formula.
Compared to exclusive breastfeeding, formula feeding is associated with greater increases in fat-free mass throughout the first year of life. Fat mass and body fat percentage tend to be lower during the first six months, but play catch-up afterward and ultimately end up higher with formula feeding than with breastfeeding.
An association was found between formula feeding, faster growth during infancy, and obesity in childhood, adolescence, and young adulthood. Some researchers suggested that the higher protein content of infant formulas was responsible, but others have argued that there are too many contributing factors (e.g., breastfeeding helps infants learn to better regulate their energy intake) to single one out.
Moreover, if the higher protein content of formulas were responsible for the infants’ accelerated growth, then how could we explain the similarities in growth between formulas containing 1.2 or 1.7 grams of protein per 100 milliliters, or between formulas containing 1.0, 1.3, or 1.5 grams of protein per 100 milliliters? (For reference, breast milk contains about 1 gram of protein per 100 milliliters.)
Still, even if consuming more protein from formulas than would be obtained from breast milk is not necessarily detrimental, it doesn’t appear to confer a benefit. There is no good reason to stray from the nutrient composition of mother’s milk during infancy, unless dealing with a preterm infant.
Preterm infants need to be fed enough protein to promote growth rates similar to those observed in healthy fetuses growing in utero. The following daily intakes have been recommended based on gestational age:
3.5–4.0 g/kg (less than 30 weeks)
2.5–3.5 g/kg (30–36 weeks)
2.5 g/kg (more than 36 weeks)
A systematic review by the Cochrane Collaboration reported greater weight gain and higher nitrogen accretion in preterm infants receiving 3.0–4.0 g/kg of protein, compared to lower daily intakes. These findings were echoed by another systematic review of 24 clinical trials.
When complementary foods are introduced to infants during the latter half of infancy, there may be a benefit to consuming more protein from meat. Compared to feeding cereal grains alongside breast milk (total protein: 1.4 g/kg/day), feeding pureed meats alongside breast milk (total protein: 2.9 g/kg/day) was shown to lead to better growth without excess fat gain.
Another study demonstrated that, as a complementary food, meat led to more favorable growth patterns than dairy (higher length-for-age and lower weight-for-length) by 12 months of age — differences that persisted at the age of 2 years. Both the meat group and the dairy group consumed the same total protein (3.0–4.0 g/kg).
During their first six months, healthy infants should consume about 1.5 grams of protein per kilogram of body weight per day (1.5 g/kg/day). This intake can be achieved exclusively through breastfeeding. From age 6 to 12 months, they should consume around 3.0 g/kg/day by using meat as complementary food. Preterm infants require 3.0–4.0 g/kg/day to facilitate catch-up growth.
The same data used to establish the RDA for infants aged 7–12 months (1.2 g/kg) was used to determine the RDA for toddlers aged 1–3 years (1.05 g/kg). The average daily protein intake of US toddlers is 4.0 g/kg, with 90% of US toddlers consuming over 3.0 g/kg.
There is a dearth of data for this age group. However, in toddlers aged 2 years with a total daily protein intake of 4.0 g/kg, complementary protein from meat led to better growth (higher length-for-age) than the same amount of complementary protein from dairy.
There is little research on what is optimal, but the average daily protein intake of US toddlers is 4 g/kg — nearly four times the RDA. Meat appears to be a better complementary food than milk.
The protein RDA is slightly higher for children (4–13 years) than for adults: 0.95 versus 0.8 g/kg. This difference makes sense considering that children are still growing and need more protein to facilitate the process. As with adults, however, the RDA may underestimate true requirements.
Use of the IAAO technique in children aged 6–11 years has suggested that around 1.5 g/kg would make for a more appropriate RDA. Protein requirements are likely higher in children involved in sports and other athletic activities.
There are no long-term studies on optimal protein intake since it would be unethical to deprive children of the protein they need for their development and various physiologic and metabolic functions.
Children require at least 1.5 grams of protein per kilogram of body weight per day (1.5 g/kg/day). An unknown amount of additional protein is likely required by children who are involved in sports or otherwise regularly active.
The protein requirements discussed so far were based on studies that used animal-based protein supplements, such as whey or egg protein supplements, or were conducted mostly in omnivores. There is no reason to believe that people who get their protein mostly or entirely from plants have inherently different protein requirements, but since plant-based proteins tend to be lower in quality than animal-based proteins, if you obtain most of your protein from plants you will need to pay attention not just to the amount of protein you eat but also to the quality of that protein.
A protein’s quality is determined by its digestibility and amino acid profile.
Digestibility matters because if you don’t digest and absorb some of the protein you eat, then it may as well not have been eaten. Animal-based proteins consistently demonstrate a digestibility rate higher than 90%, whereas proteins from the best plant-based sources (legumes and grains) show a digestibility rate of 60–80%.
Plants contain anti-nutrients that inhibit protein digestion and absorption, such as trypsin inhibitors, phytates, and tannins. While cooking does reduce anti-nutrient concentrations, it doesn’t eliminate them entirely. Plant-based protein powders, however, are mostly free of antinutrients and so have digestibility rates similar to those of animal-based proteins.
The amino acid profile of a protein matters because all proteins, including the protein you eat and the protein in your body, are made from some combination of 20 amino acids (AAs). Your body can produce 11 of these AAs, making them nonessential amino acids (NEAAs). Your body cannot produce the other 9, which are therefore essential amino acids (EAAs) you must get through food.
Building muscle requires that, cumulatively, muscle protein synthesis (MPS) exceeds muscle protein breakdown (MPB), resulting in a net accumulation of muscle protein. All 20 AAs are required to build muscle tissue, but MPS is stimulated primarily by the EAAs in the food you ingest.
Plant-based proteins, whether from whole foods or protein powders, contain less EAAs than animal-based proteins.
In particular, plant-based proteins are lower in the EAA leucine, which is believed to act as a signal to “turn on” anabolic signaling pathways and MPS, although all EAAs are required for the effect to persist.
The lower leucine and EAA content of plant-based proteins helps explain why several studies have reported lower rates of MPS from soy protein powders and beverages than from whey protein, skim milk, whole milk with cheese, and lean beef.
However, while differences in MPS do appear to translate to differences in lean mass when modest supplemental protein doses are used (about 20 g/day), when higher doses are used (33–50 g/day), animal-based (whey) and plant-based (soy, rice) supplemental proteins appear to affect lean mass similarly. In short, consuming more protein overall appears to offset the lower quality of the plant-based proteins.
Plant-based proteins also contain limiting amino acids, which are EAAs present in such small amounts that they bottleneck protein synthesis. Lysine is the most common limiting amino acid, especially in cereal grains, such as wheat and rice. Nuts and seeds also tend to have lysine as a limiting amino acid. Beans and legumes, on the other hand, contain sufficient lysine but lack sulfurous amino acids, such as methionine and cysteine. Combining different plant-based proteins can help make up for their respective deficits.
Plant-based proteins are of lower quality (they are less bioavailable and contain less EAAs). If you get most of your protein from plants, you will need to consume more protein to achieve the same muscle growth as someone with a more omnivorous diet.
The simplest method to overcome the EAA deficits of a plant protein is to eat more of it. As aforementioned, a handful of studies have shown that large doses (33–50 g/day) of animal-based (whey) and plant-based (soy, rice) supplemental proteins appear to increase lean mass similarly.
Another way to overcome the EAA deficits of plant proteins is to combine complementary EAA profiles. Historic examples of such combinations include beans with corn in the Americas and rice with soybean in Asia. These grain-legume combos work because legumes supply the lysine missing in grains whereas grains supply the methionine and cysteine missing in legumes.
Adapted from: Woolf et al. PLoS One. 2011.
Unfortunately, most plant proteins are low in leucine, meaning that combining different plant proteins will not have a large benefit unless one of those proteins is corn protein (whose leucine content rivals that of whey protein).
If your protein has less leucine, you need to eat more of it to maximize MPS — or you can take leucine as a supplement. MPS was increased similarly by 25 grams of whey protein (providing 3 grams of leucine) and by a combination of 6.25 grams of whey protein and 4.25 grams of supplemental leucine (5 grams of leucine in total). A rodent study using plant proteins reported similar results.
The EAA deficits of plant-based proteins can be overcome by eating more, combining complementary proteins, and supplementing with leucine.
Muscle protein synthesis (MPS) is the process of building new skeletal muscle tissue. When MPS chronically exceeds muscle protein breakdown (MPB), resulting in a positive net protein balance, we can expect muscle growth over the long term. Each time you eat represents an opportunity to promote muscle growth through the stimulation of MPS.
Protein-feeding studies using various doses of whey protein suggest that 0.24 g/kg/meal will maximize the MPS of the average young adult, whereas 0.40 g/kg/meal will maximize the MPS of most young adults. For older adults, these two values jump to 0.40 and 0.60 g/kg/meal.
|Body weight (lb)||Body weight (kg)||20s||30s, 40s, 50s||≥60|
The ranges in this table represent individual variations. The minimum protein requirements increase as you age, but to what degree is uncertain because of the age gap left by the studies: most subjects were in their 20s (0.24–0.40 g/kg) or 60s/70s (0.40–0.60 g/kg). For people in their 30s, 40s, or 50s, the 0.29–0.53 g/kg range reflected in this table is an educated guess.
References: Schoenfeld and Aragon. J Int Soc Sports Nutr. 2018.  Rafii et al. J Nutr. 2016.  Morton et al. Front Physiol. 2015.  Moore et al. J Gerontol A Biol Sci Med Sci. 2015.  Rafii et al. J Nutr. 2015. 
Your mileage may vary. The ranges above are not ideal ranges. Instead, they cover the known extent of interindividual variations among healthy adults. In other words, if you’re in your 20s, you don’t need to calculate your protein intake per meal so that it falls precisely within the 0.40–0.60 g/kg range. Rather, your minimum protein intake per meal (to maximize MPS) is likely to fall within that range.
Further, there are at least three good arguments in favor of eating toward or even above the higher end of your range:
First, the ranges we listed are derived from studies using whey protein in isolation. Whey protein is highly bioavailable, rich in essential amino acids (EAAs), and quickly digested. When eating lower-quality or slower-digesting proteins (as would occur when eating a meal, especially one rich in plant-based foods), higher protein intakes are probably required.
Second, while these values suggest a protein-intake threshold for maximally stimulating MPS, there is no known threshold for whole-body protein balance. For example, a study using meals with lean beef found that 40 and 70 grams of protein (0.5 and 0.8 g/kg) led to similar increases in MPS, but that 70 grams led to greater increases in whole-body protein synthesis and greater decreases in whole-body protein breakdown. In other words, eating more protein may not necessarily translate to greater muscle-protein turnover and growth, but since muscle tissue accounts for only 25–30% of whole-body protein turnover, the additional protein is not “wasted” (a common myth).
Third, as shown above in the Prevalence of sarcopenia by age and sex in the US graphic, even people in their twenties can suffer from sarcopenia — in which case they would benefit from a protein intake closer to the one recommended in this table for adults over sixty.
You may have heard that if you eat more than 30 grams of protein in one sitting, the “excess” will pass undigested, but that’s just a myth. It is however true that spreading your protein intake over a few meals, making sure that you meet your desirable minimal protein intake per meal with each meal, will generally result in greater lean mass and strength. A pragmatic review article suggests that, to maximize their lean mass, active adults should consume 1.6–2.2 g/kg/day spread across four meals (0.40–0.55 g/kg/meal).
For maximal stimulation of muscle protein synthesis, aim for a per-meal dose of quality protein (such as can be found in meat, eggs, and dairy) of 0.4–0.6 g/kg. Higher doses will not be wasted and are probably necessary when eating mixed meals that contain a variety of protein sources.
After exercising, when your muscles are more sensitive to the anabolic effect of protein, take a dose in the range of your desirable minimal protein intake per meal. If you’ve been exercising on an empty stomach, you’ll be in negative protein balance, so take this dose as soon as possible. Otherwise, try to take it within a couple of hours — the exact size of your “window of opportunity” depends on how much protein you’re still digesting.
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