It’s an age-old debate: how much protein should we be eating in a single meal?
For years, popular magazine (and internet) folklore suggested that anything over 20-30g in a meal was a “waste.” That number was arbitrary. No science ever supported the idea that there was a useful within-meal limit for protein intake.
However, a few years back, two particular studies were designed to answer this very question. Well, sort of.
What Does the Research Say?
The first study showed that when college-aged weight-trainers drink 0g, 5g, 10g, 20g, or 40g of protein after a weight training session, muscle protein synthesis is stimulated maximally at the 20g dose. Interestingly, there were no further increases in muscle protein synthesis at the 40g dose.
The second study showed that when young and elderly volunteers were given 30 or 90g of dietary protein in a single meal, the 30g dose maximally stimulated muscle protein synthesis. Again, there were no further increases in muscle protein synthesis at the 90g dose.
Case Closed? Or Is It?
Oddly, since the publication of those two studies, most fitness pros have closed the book on this topic of per meal protein needs. Articles have been written, minds have been made up. Indeed, some authors have even suggested that we’re ignorant wastrels if we dare eat more than 20-30g of protein in a single sitting.
But wait just a second. What did those two studies actually show?
They showed that at 20-30g in a single meal, protein synthesis is maximally stimulated. Which raises an important question: Is muscle protein synthesis the only reason we eat protein? Actually, no.
Protein Synthesis and Breakdown
In a more recent review, Dr. Robert Wolfe, one of the top protein researchers in the world, argues that, while the muscle protein synthesis information above is interesting, it’s essentially useless when planning lunch.
You see, 20-30g of protein at a single meal does max out protein synthesis. The studies are clear on that one. However, what this information misses is that protein anabolism is a function of protein synthesis and breakdown. And, according to the research, protein breakdown is slowed with ever-increasing amounts of protein in a single meal. In other words, “there doesn’t appear to be a practical upper limit to the anabolic response to protein in a single meal.” (Quoted from Dr. Wolfe).
So, if you eat a big protein meal, that extra protein isn't "wasted." Instead, it creates a scalable anabolic response in proportion to the intake. It does this by suppressing protein breakdown. By extension, whether you eat small protein meals spread throughout the day, or you eat just a few big protein meals a day, assuming intake is the same, you may benefit from the same anabolic response.
And yes, this claim is backed up by research too.
Check out this study for more. In it, when 80% of the daily protein intake was eaten in a single meal – as much as 100g of protein eaten at once - it was more anabolic than spreading the same amount of protein throughout the day. In essence, large, infrequent protein meals were more anabolic in this study vs. small, frequent protein meals. Of course, as with all research, the data are mixed. Some studies show this effect. Others do not. However, the take-home message is the same: if you actually look at the full body of research, it becomes clear that there’s not really a practical upper limit of protein intake for optimizing muscle protein. So much for the 20-30g myth.
Remember, Muscle Isn’t Everything
Beyond this very narrow view of protein intake (muscle protein synthesis vs. breakdown), there’s a much more important question at stake: why else do we eat protein?
You see, there are other benefits to eating protein beyond muscle building. There’s satiety, the thermogenic effects, the impact on the immune system, and more (see below). Plus, there are probably a few benefits science can’t measure yet. I say the last part because there’s so much experiential evidence suggesting that when you’re training hard and you up your protein intake, you do better. So maybe we just haven’t looked in the right places to notice the real benefits.
Other Protein Benefits
We shouldn’t look at the world through a straw (i.e. see one protein study on one isolated topic and make broad generalizations). So, to help us remember that, let’s review a list of benefits we get from eating extra protein.
- Increased thermic effect of feeding – While all macronutrients require metabolic processing for digestion, absorption, and storage or oxidation, the thermic effect of protein is roughly double that of carbohydrates and fat. Therefore, eating protein is actually thermogenic and can lead to a higher metabolic rate. This means greater fat loss when dieting and less fat gain during overfeeding/muscle building.
- Increased glucagon – Protein consumption increases plasma concentrations of the hormone glucagon. Glucagon is responsible for antagonizing the effects of insulin in adipose tissue, leading to greater fat mobilization. In addition, glucagon also decreases the amounts and activities of the enzymes responsible for making and storing fat in adipose and liver cells. Again, this leads to greater fat loss during dieting and less fat gain during overfeeding.
- Metabolic pathway adjustment –When a higher protein (20-50% of intake) is followed, a host of metabolic adjustments occur. These include: a down-regulation of glycolysis, a reduction in fatty acid synthesis enzymes, and an increase in gluconeogenesis - a carbohydrate “draining” effect where carbons necessary for ridding the body of amino nitrogen is drawn from glucose.
- Increased IGF-1 – Protein and amino-acid supplementation has been shown to increase the IGF-1 response to both exercise and feeding. Since IGF-1 is an anabolic hormone that’s related to muscle growth, another advantage associated with consuming more protein is more muscle growth when overfeeding and/or muscle sparing when dieting.
- Reduction in cardiovascular risk – Several studies have shown that increasing the percentage of protein in the diet (from 11% to 23%) while decreasing the percentage of carbohydrate (from 63% to 48%) lowers LDL cholesterol and triglyceride concentrations with concomitant increases in HDL cholesterol concentrations.
- Improved weight loss profile – Research by Layman and colleagues has demonstrated that reducing the carbohydrate ratio from 3.5 – 1 to 1.4 – 1 increases body fat loss, spares muscle mass, reduces triglyceride concentrations, improves satiety, and improves blood glucose management
- Increased protein turnover — All tissues of the body, including muscle, go through a regular program of turnover. Since the balance between protein breakdown and protein synthesis governs muscle protein turnover, you need to increase your protein turnover rates in order to best improve your muscle quality. A high protein diet does just this. By increasing both protein synthesis and protein breakdown, a high protein diet helps you get rid of the old muscle more quickly and build up new, more functional muscle to take its place.
- Increased nitrogen status — A positive nitrogen status means that more protein is entering the body than is leaving the body. High protein diets cause a strong positive protein status and when this increased protein availability is coupled with an exercise program that increases the body’s anabolic efficiency, the growth process may be accelerated.
- Increased provision of auxiliary nutrients — Although the benefits mentioned above have related specifically to protein and amino acids, it’s important to recognize that we don’t just eat protein and amino acids — we eat food. Therefore, high protein diets often provide auxiliary nutrients that could enhance performance and/or muscle growth. These nutrients include creatine, branched chain amino acids, conjugated linoleic acids, and/or additional nutrients that are important but remain to be discovered. And don’t forget the vitamins and minerals we get from protein rich foods.
(And lest anyone think I’m a shill for the protein powder industry, this last point clearly illustrates the need to get most of your protein from food, rather than supplements.)
Looking over this list of benefits, it’s hard to ignore the fact that we don’t just eat protein for its muscle synthetic effect. We eat protein for a bunch of other reasons too. Since a higher protein diet can lead to a better health profile, an increased metabolism, improved body composition, and an improved training response, why would anyone ever try to limit their protein intake to the bare minimum?
It seems to me that whether someone’s on a hypoenergetic diet (low calorie) or a hyperenergetic diet (high calorie), the one macronutrient they would want to be sure to “overeat” (relatively speaking) would be protein.
But that’s not what people do, is it?
Instead, they look for the bare minimum of protein (whether it’s 20-30g/meal or 0.8g/kg/day), and then overeat carbohydrates and fats instead. That could prove to be a performance – and body composition – mistake.
So here’s my recommendation for men and women interested in losing fat, gaining lean muscle, and improving their health and performance:
- Women – Eat 1 palm-sized portion of lean, complete protein (about 20-30g) with each meal, every few hours. If you eat less frequently, eat a bit more protein with each meal. If you eat more frequently, eat a bit less protein with each meal.
- Men – Eat 2 palm-sized portions of lean, complete protein (about 40-60g) with each meal, every few hours. If you eat less frequently, eat a bit more protein with each meal. If you eat more frequently, eat a bit less protein with each meal.
This pattern of intake will make sure you’re getting enough protein to reap all the benefits that this amazing macronutrient has to offer.
Dr. John Berardi is the co-founder of Precision Nutrition and the co-creator of the Precision Nutrition Certification program. For more from Dr. Berardi, check out this free 5-day course exclusively for fitness professionals “The Essentials of Exercise and Fitness Nutrition”.