We all know that protein is important. After water, protein is by far the largest component of your body, making up about 20 percent of your muscle and organ tissue, including 10 percent of your brain. It’s in every cell of your body, and is a primary building material for your skin, bones, and everything in between.

Unlike the other two macronutrients, carbohydrates and fat, little of the protein you eat is used for energy. Instead, it’s used to build, repair, and replace the protein in your cells, which breaks down throughout the day. Exercise accelerates protein turnover, especially in your muscle cells. That’s why athletes and fitness enthusiasts need to pay special attention to the amount of protein in their diets, as well as the quality of that protein. It’s crucial for muscle size and strength, body composition, and sports performance.

In this special report, I’m going to cover these topics:

  • How much protein you need
  • How protein helps with weight control and improves body composition
  • The safety and potential side effects of a high-protein diet
  • Which types of protein are best for your goals
  • How to choose the best protein supplements
  • How to use protein supplements before and after workouts, and at other times of day

This information is useful for anyone interested in health and fitness, from high-level competitive athletes to recreational enthusiasts. It has everything you need to know about protein, and nothing you don’t.


No one really knows how much protein you need each day, whether “you” refers to people in general or to the individual and unique “you” who happens to be reading this. Even if we get as specific as possible regarding age, size, body composition, gender, activity level, habitual diet, and goals, the best we can do is provide a range.

My friend Jose Antonio, Ph.D., is one of the world’s leading experts in sports nutrition and supplementation. He offers these reasons why we’ll never have a formula that applies to everyone:

  • Two people consuming the same absolute amount of protein could consume different amounts and types of amino acids. There are 20 different amino acids, 10 of which are considered “essential,” meaning your body can’t make them from other proteins. Different foods and supplements contain different amino acids in different proportions to each other.
  • When you eat protein alters the way your body uses it.
  • The content and volume of the other foods you eat also affect the way your body uses protein.

Without a precise equation that tells us how much protein an athlete should consume, I fall back on a very simple recommendation for all the athletes I train: eat 1 gram of protein per pound of body weight per day. I’ve used this strategy for years with great success. The success isn’t because I’ve somehow figured out a magic formula that’s eluded scientists. It’s because it’s simple to follow and easy to remember.

Some would argue that this is an awful lot of protein. It’s more than twice the RDA and even higher than the recommended range for strength athletes, which tops out at 0.9 grams of protein per pound of body weight. I agree. It is a lot of protein. It’s more than anyone needs for building and repairing muscle tissue.

I think it’s better to consume too much protein rather than risk not eating enough. Why? Because protein does more than build and repair tissues. It increases your metabolism, reduces hunger, and helps you preserve muscle tissue during times when you’re cutting back on total calories with the goal of losing body fat.

The studies cited in the next section shed light on why this is.


The following studies compared higher- and lower-protein diets.

The first, published in 2010, shows that a high-protein diet prevents muscle loss in young, resistance-trained athletes who are trying to lose weight. The 20 subjects cut their habitual food intake by 40 percent for two weeks, while following their normal training. One group got 35 percent of their calories from protein, while the other got just 15 percent.

There was no difference in performance in either group. But those who had the higher- protein diet lost twice as much total weight, on average, while retaining virtually all of their lean mass. Those on the lower-protein diet lost 3.5 pounds of muscle, on average.

Still, the study showed this wasn’t an ideal diet for either group. Those getting more protein reported higher fatigue from their workouts, despite losing more weight.

Mettler S et al, Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc
2010; 42 (2): 326-337.

In a much bigger study published in 2008, 158 obese individuals, from 25 to 50 years old, cut 500 calories a day from their normal diets for 12 weeks. One group got a protein supplement called ProlibraTM twice a day, while the other got a placebo drink (same calories, but without the protein). The supplement is dairy-based, meaning it has high concentrations of calcium and leucine (an essential amino acid).

Both groups lost weight, which makes sense with a 500-calorie-a-day deficit. But those  who got the protein supplement lost more fat and less lean tissue.

Frestedt JL et al, A whey-protein supplement increases fat loss and spares lean muscle in obese subjects: a randomized
human clinical study. Nutr Metab 2008; 5: 8.

A 2003 review made several key points:

People who eat high-protein diets ad libitum—that is, as much as they want—will lose  body fat while retaining muscle fat because the protein improves satiety while also burning more calories during digestion. So you eat less total food, but you also burn off more of the food you eat. This effect carries over to the post-weight-loss period, when the goal is to maintain the new, lower body weight. Since you’ve preserved more muscle, your metabolic rate will be higher, which helps you keep your weight in check.

Westerterp-Plantenga MS, The significance of protein in food intake and body weight regulation. Curr Opin Clin Nutr
Metab Care 2003; 6 (6): 635-638.

A 2004 study recruited obese patients with type 2 diabetes, putting half on a low- protein diet and half on high protein for 64 weeks. Weight loss was similar (although the high-protein group lost more), but when they regained weight during the follow-up period, the low-protein group saw their blood pressure rise more. The researchers concluded: “A high-protein weight-reduction diet may provide a more favorable cardiovascular risk profile than a low-protein diet with similar weight reduction in people with type 2 diabetes.”

Brinkworth GD et al, Long-term effects of advice to consume a high-protein, low-fat diet, rather than a conventional weight-loss diet, in obese adults with type 2 diabetes: one-year follow-up of a randomized trial. Diabetologia 2004; 47 (10): 1677-1686.

In a more radical study, published in 2004, researchers recruited 148 male and female subjects (average age: 44; BMI: 29.5; 37% body fat) and put them on a 500-calorie- per-day diet for four weeks.

They then followed them over the next three months, with half getting 18% of their calories from protein and the other getting 16%. The difference was an extra 48 grams a day for the higher-protein group. The results: “A 20% higher protein intake … during weight maintenance after weight loss resulted in a 50% lower body-weight regain that consisted of fat-free mass. This was related to increased satiety and decreased energy efficiency.”

In other words, that small difference in dietary protein resulted in a big difference not just in weight regain, but in what type of weight was regained. More protein meant more muscle.

Westerterp-Plantenga  MS et al, High protein intake sustains weight maintenance after body weight loss in humans. Int J Obes Relat Metab Disord. Jan 2004; 28 (1): 57-64.

In a 2005 study from the same team, a similar research population was followed for six months following an initial four-week crash diet. This time the higher-protein group got 30 grams per day above the control group. The researchers found: “During weight maintenance, the protein group showed a higher protein intake (18% vs. 15% of calories), a lower weight regain, and a decreased waist circumference compared with the control group. Weight regain in the protein group consisted of only fat-free mass, whereas the control group gained fat mass as well.” This was partly attributed to the higher-protein group being less hungry than the others.

Lejeune MP et al, Additional protein intake limits weight regain after weight loss in humans. Br J Nutr. Feb 2005; 93 (2): 281-289.

In a 2009 study, the same group (from Maastricht University in the Netherlands), assessed the 24-hour response to two types of isocaloric feedings on healthy men and women:

  • Group 1 consumed 60% carbs, 30% fat, and 10% protein
  • Group 2 consumed 40% carbs, 30% fat, and 30% protein

The researchers found multiple benefits of higher protein diets, such as:

  • Increased energy expenditure
  • Increased fat oxidation
  • Higher protein anabolism in men
  • Increased satiety in women

Westerterp-Plantenga  MS et al, Sex differences in energy homeostasis following a diet relatively high in protein exchanged with carbohydrate, assessed in a respiration chamber in humans. Physiol Behav. 2009; 97 (3-4): 414-419.


Thermic effect of food, or TEF, describes the energy expended by our bodies in order to consume (bite, chew, and swallow) and process (digest, transport, metabolize, and store) food. Certain foods require us to burn more calories than others.

Fat, for example, is very simple to digest. Your body simply breaks down the fat molecules into smaller and smaller bits. You’ll burn up to 3% of the fat calories you consume through TEF.

Carbohydrates take more effort to digest because your body needs to break them down into simple sugars and convert them to glucose molecules. You’ll burn anywhere from 5 to 10% of the calories through TEF.

Protein requires the most work to digest because it’s made up of as many as 20 amino acids. Your body has to break down that protein in your steak or peanut butter into its component amino acids, then reform them into molecules it can use for its many functions. You’ll burn 20 to 30% of protein calories through TEF.

A gram of protein has 4 calories, which means that in a meal with 25 grams of protein, you may end up burning 25 calories just through TEF.

Tappy L, Thermic effect of food and sympathetic nervous system activity in humans. Reprod Nutr Dev. 1996; 36 (4): 391-7.

The combination of satiety (you’re less hungry in the hours following a protein-rich meal) and TEF shows why higher-protein diets are so effective for weight loss. Moreover, adding protein to your diet following weight loss is a proven strategy for limiting the amount of weight you regain. The weight you do add will mostly be lean tissue—muscle, bone, and everything else that isn’t fat.

So what’s the catch, you may ask. As you’ll see in the next section, there isn’t one.


Spend enough time in the fitness or nutrition field, and you’re sure to hear someone wave a caution flag, warning you that a high-protein diet is dangerous to your kidneys.“This is perhaps the longest-enduring myth in the sports nutrition field,” Dr. Antonio says. “The notion that eating more protein than the paltry recommended daily allowance will result in renal problems has no foundation in scientific fact or support.”

In a 2000 study, researchers looked at bodybuilders and other well-trained athletes whose protein intake was judged to be either high or medium, relative to their body weight. They took blood and urine samples to see if there were signs of kidney problems.

The researchers found that the athletes’ nitrogen balance became positive (that is, they had enough protein to build new muscle tissue) when their daily intake exceeded 1.26 grams of protein per kilogram of body weight, or 0.57 grams per pound. They saw no link between protein intake and creatinine clearance, albumin excretion rate, or calcium excretion rate, any of which, if elevated, would suggest that a higher-protein diet was potentially dangerous.

Their conclusion: “Protein intake under 2.8 grams of protein daily per kilo (2.2lbs) of body weight does not impair renal function in well-trained athletes, as indicated by the measures of renal function used in this study.”

Poortmans JR and Dellalieux O, Do regular high-protein diets have potential health risks on kidney function in athletes? Int J Sport Nutr Exerc Metab. 2000; 10 (1): 28-38.

In a 2005 study, the researchers suggested that “while protein restriction may be appropriate for treatment of existing kidney disease, 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.”

Martin WF et al, Dietary protein intake and renal function. Nutr Metab. 2005; 2: 25.

Another question that arises: Is a high-protein diet harmful to your bones? Not only is it based on a myth, it’s a completely backwards myth. “Oddly enough, not enough protein is deleterious to your bone health,” Dr. Antonio says.

A 2002 study concluded that “excess protein will not harm the skeleton if the calcium intake is adequate,” while a review study published in 2003 showed that people with chronically low protein consumption were at higher risk for lower bone density and more bone loss.

Heaney RP, Effects of caffeine on bone and the calcium economy. Food Chem Toxicol. 2002; 40 (9): 1263-70. Kerstetter JE et al, Low protein intake: the impact on calcium and bone homeostasis in humans. J Nutr. 2003; 133 (3): 855S-861S.

A 1998 study worth noting found that protein supplements help elderly folks heal faster from bone-related injuries. They looked specifically at femoral fractures—the large leg bone that connects with the pelvis to create the hip joint—and found that supplementing with 20 grams of protein a day reduced bone loss and allowed seniors to return home sooner from rehabilitation facilities.

Porter KH and Johnson MA, Dietary protein supplementation and recovery from femoral fracture. Nutr Rev. 1998 Nov; 56 (11): 337-40.


So far we’ve seen that a higher-protein diet is both safe and beneficial. You’ll have greater satiety from one meal to the next, a faster metabolism due to TEF, and more muscle with less fat. All those benefits, with no adverse side effects. But not all protein-rich foods are equally beneficial. Let’s start by comparing the protein in animal foods vs. vegetables.

We know that eggs, dairy, beef, pork, and poultry are all terrific sources of protein. Vegetables with some protein include soy, nuts and seeds, legumes, and whole grains.

A 1999 study came to this conclusion: “Consumption of a meat-containing diet contributed to greater gains in fat-free mass and skeletal muscle mass with resistance training in older men than did a lactoovovegetarian diet.”

Campbell WW et al, Effects of an omnivorous diet compared with a lactoovovegetarian diet on resistance-training- induced changes in body composition and skeletal muscle in older men. Am J Clin Nutr. 1999; 70 (6): 1032-1039.

A 2005 study compared low-fat milk to soy protein for building muscle. The conclusion: “In young men completing 12 weeks of resistance training (5d/wk), we observed a tendency (P = 0.11) for greater gains in whole-body lean mass and … greater muscle fiber hypertrophy with consumption of milk.”

Phillips SM et al, Dietary protein to support anabolism with resistance exercise in young men. J Am Coll Nutr. 2005 Apr; 24 (2): 134S-139S.

Another question that I hear often: Is it better to have whole milk or skim? Old-school bodybuilders would drink as much as a gallon a day of whole milk back in the days before steroids (or creatine, for that matter). But most of us grew up with a fear of fat, however unfounded. Thus, skim milk replaced whole milk as the muscle-building fluid of choice (assuming protein supplements, which are usually made from milk proteins, aren’t an option at the moment).

In a 2006 study, researchers compared the two. Although they used small amounts of both types of milk, giving most of their subjects just 8 grams of post-workout protein, they found enough of a difference to suggest that “whole milk may have increased utilization of available amino acids for protein synthesis.”

Elliot TA et al, Milk ingestion stimulates net muscle protein synthesis following resistance exercise. Med Sci Sports Exerc. 2006; 38 (4): 667-674.

Now let’s look at which milk protein is better.


You’ll find lots of research here on the question of which milk protein is best for building muscle. It really depends on when you’re having the supplement in relation to your workout.

First let’s look at whey.

A 2011 study from the U.S. Department of Agriculture found that supplementing with 60 grams a day of whey protein for 6 months resulted in less body weight and body fat, a smaller waist size, and a reduction in ghrelin, a hunger-triggering hormone.

Baer DJ et al, Whey protein but not soy protein supplementation alters body weight and composition in free-living overweight and obese adults. J Nutr. 2011; 141 (8): 1489-1494.

A 2004 study found that whey protein produces an immediate rise in the amino acid pool following resistance exercise. That’s followed by a second rise 90 minutes later.

Borsheim E et al, Effect of an amino acid, protein, and carbohydrate mixture on net muscle protein balance after resistance exercise. Int J Sport Nutr Exerc Metab. 2004; 14 (3): 255-271.

A 2007 study found that 20 grams of a supplement combining whey protein and free amino acids up-regulated protein synthesis and anabolism when compared to a carbohydrate-only drink. The researchers gave the subjects the supplement an hour before and an hour after training. The subjects receiving the supplement showed increases in body mass, fat-free mass, thigh mass, muscle strength, serum IGF-1, IGF-1 mRNA, myosin heavy chain I and IIa expression, and myofibrillar protein.

The researchers concluded: “Ten weeks of resistance training with 20 grams of protein and amino acids ingested 1 hour before and after exercise is more effective than carbohydrate placebo in up-regulating markers of muscle protein synthesis and anabolism along with subsequent improvements in muscle performance.”

Willoughby DS et al, Effects of resistance training and protein plus amino acid supplementation on muscle anabolism, mass and strength. Amino Acids 2007; 32 (4): 467-477.

Now let’s look at comparisons of whey with casein.

In a study published in 2000, the researchers cut calories by about 20% in three different groups of subjects. One group simply dieted. The other two groups dieted, trained, and received a supplement of either casein or whey protein. The casein-supplemented group did far better than the group that got whey. They lost almost three times as much fat and doubled their strength gains. The conclusion: “This significant difference in body composition and strength is likely due to improved nitrogen retention and overall anticatabolic effects caused by the peptide components of the casein hydrolysate.”

Demling RH and DeSanti L, Effect of a hypocaloric diet, increased protein intake and resistance training on lean-mass gains and fat-mass loss in overweight police officers. Ann Nutr Metab. 2000; 44 (1): 21-29.

A 2004 study compared whey and casein and concluded that whey and casein offer similar muscle-building benefits. They used a 20-gram supplement of whey or casein an hour after training. Whey produced a greater net balance of leucine (an essential amino acid considered to have the greatest anabolic potential) over time.

The researchers concluded: “Acute ingestion of both whey and casein after exercise resulted in similar increases in muscle protein net balance, resulting in net muscle protein synthesis despite different patterns of blood amino acid responses.”

Tipton KD et al, Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise. Med Sci Sports Exerc. 2004; 36 (12): 2073-2081.

A 2000 study showed that whey protein, combined with branched-chain amino acids and glutamine, improves body composition by increasing lean mass and possibly decreasing fat mass. The researchers concluded: “This study suggests that whey protein combined with BCAA and glutamine leads to improved body composition (increased lean muscle mass) and resistance exercise performance. Whey protein supplementation may help decrease body fat.”

Colker CM et al, Effects of supplemental protein on body composition and muscular strength in healthy athletic male adults. Current Therapeutic Research 2000; 61 (1): 19-28.

A 1997 study showed that whey protein induces a dramatic (68%) but short increase in plasma amino acids, vs. 31% for casein. But casein inhibited muscle-protein breakdown by 34%, an effect that wasn’t found for whey. Over 7 hours, leucine balance was higher for casein.

Boirie Y et al, Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci. 1997; 94 (26): 14930-14935.

However, a 2003 study found that for older men, faster-acting whey is a better choice than casein: The conclusion: “[D]uring aging, protein gain was greater with whey (rapidly digested protein), and lower with casein (slowly digested protein). This suggests that a ‘fast’ protein might be more beneficial than a ‘slow’ one to limit protein losses during aging.

Dangin M et al, The rate of digestion affects protein gain differently during aging in humans. J Physiol. 2003; 549 (2): 635-644.

Now let’s look at some other important benefits you may get from whey protein. I mentioned bone health earlier. A 1996 study offered this conclusion: “We propose the possibility that the active component in the whey protein plays an important role in bone formation by activating osteoblasts.”

Takada Y et al, Whey protein stimulated the proliferation and differentiation of osteoblastic MC3T3-E1 cells. Biochem Biophys Res Commun. 1996; 223 (2): 445-449.

Glutathione is among the body’s most powerful antioxidants. But extreme exercise lowers it, making the body more vulnerable to rogue chemicals that can lead to damage at the cellular level. A 2004 study came to this conclusion: “This study demonstrated that whey protein supplementation lessens the decreases in glutathione caused by prolonged exercise.”

Middleton N et al, Whole blood and mononuclear cell glutathione response to dietary whey protein supplementation in sedentary and trained male human subjects. Inter J Food Sci Nutr 2004; 55 (2): 131-141.

Then there’s a potential stress-reduction benefit, according to a 2002 study: “Because an increase in the plasma Trp-LNAA ratio is considered to be an indirect indication of increased brain serotonin function, the results suggest that dietary protein rich in alpha- lactalbumin improves cognitive performance in stress-vulnerable subjects via increased brain tryptophan and serotonin activities.”

Markus CR et al, Whey protein rich in alpha-lactalbumin increases the ration of plasma tryptophan to the sum of the other large neutral amino acids and improves cognitive performance in stress vulnerable subjects. Am J Clin Nutr. 2002; 75 (6): 1051-1056.

The same research group, in a 2005 study, found that taking alpha-lactalbumin (a whey fraction) in the evening increases alertness and attention the following morning, especially in poor sleepers. The researchers’ conclusion: “Evening dietary increases in plasma tryptophan availability for uptake into the brain enhance sustained alertness early in the morning after an overnight sleep, most likely because of improved sleep.”

Markus CR et al, Evening intake of alpha-lactalbumin increases tryptophan availability and improves morning alertness and brain measures of attention. Am J Clin Nutr. 2005; 81 (5): 1026-1033.

Which milk protein works best for you probably comes down to questions of timing and absorption. Whey is faster acting, working its way through your digestive system in about 3 hours. For casein, it’s more like 7 hours.

My recommendations:

  • About 30 to 60 minutes before your workout, have a protein shake with 20 grams of a whey isolate supplement.
  • About 30 minutes post-workout, have a shake made with at least 30 grams of a casein-rich protein supplement.

Earlier I mentioned a 1997 study by Boirie et al. The researchers determined that whey will cause amino acid levels to peak about 60 to 90 minutes post-ingestion, which means that if you use whey as your pre-workout supplement, you’ll have the maximum amount of amino acids available to your muscles right in the middle of your workout, when you can use them.

But after a workout, casein appears to be superior, keeping amino acids elevated for up to 7 hours. Casein is especially beneficial if you work out in the evening, and will be going to bed soon after. Even on non-workout days, Dr. Antonio says it’s a good idea to have a casein supplement before bed to take advantage of the prolonged elevation in amino acid levels.


Here’s what we’ve learned:

  • No one knows exactly how much protein you can use at any given time or on any given day. There are too many variables to calculate.
  • In general, though, more protein in your diet is better than less, especially when your primary goal is body composition—maximum muscle, minimum fat. I recommend a daily target of 1 gram of protein per pound of body weight.
  • Unless you have existing kidney disease, there’s no reason to think a high- protein diet is dangerous.
  • The real danger to your health comes from a low-protein diet. It’s bad for your body composition, bone density, and metabolism.
  • Animal proteins (dairy, eggs, meat) are superior to vegetable proteins (soy, beans, grains) for building muscle.
  • Most protein supplements will have a predominance of either casein or whey, both of which are milk proteins and both of which are beneficial.
  • Because whey is faster to digest, it makes amino acids available to your muscles faster. Thus, whey is the better choice as a pre-workout supplement. Amino acid levels will peak about 60 to 90 minutes after drinking a pre-workout protein shake made from whey isolates.
  • Casein is slower to digest, giving you a supply of amino acids for 7 hours following ingestion. Thus, casein is a better post-workout supplement. It’s also a good choice before you go to sleep at night.