The Ultimate Guide to Protein, Part II

Lyle McDonald

Lyle McDonald is a physiologist and author who has spent over a decade obsessively finding ways to apply cutting-edge scientific research to sports nutrition, fat loss and muscle growth.

The Ultimate Guide to Protein, Part I

Q. We hear a lot about the importance of taking in protein as soon as possible after exercise. How true is this?

A. Another yes and no kind of answer. The original idea of a window of opportunity for nutrient intake actually came out of endurance research, scientists become fascinated about how to improve glycogen synthesis following training. A zillion studies were done and one factor that was important was timing, under certain conditions, how quickly you got nutrients into the system was critical in terms of overall glycogen synthesis rates.

This became a little more relevant to strength athletes when some research showed that protein plus carbs worked better than carbs alone for glycogen synthesis. More research followed, some of it found a benefit of protein, others didn't.

Finally, researchers started looking at resistance training. Various studies examined different combinations of nutrients, often using isolated essential amino acids (EAA) with or without carbs (usually sucrose). Many found that it was absolutely crucial that nutrients be consumed following training to switch the body from a net catabolic state (breaking down more protein than it was synthesizing) to a net anabolic state (the opposite).

But these studies all suffered one huge methodological problem: they were done in the fasted state. Basically, take subjects, have them not eat overnight, bring them to the lab, train them, feed or don't feed them and see what happens. And under those conditions, absolutely consuming post-workout nutrients is critical.

I'd note that one study, tested under the same conditions, actually found that pre-workout aminos worked better than post-workout. This makes some logical sense mind you, consuming amino before a morning fasted workout will have them in your bloodstream during and after training faster than consuming them afterwards.

But the question then became this: If you're not training first thing in the morning fasted and have eaten a solid meal 2-3 hours before training, does this still hold?

Consider my response to a previous question where I pointed out that a whole-food meal will continue digesting for up to 5-6 hours, maintaining an anabolic state. If you've eaten a solid meal 2-3 hours before workout, you have plenty of nutrients floating around in the bloodstream. Will post-workout nutrition be as crucial?

A recent area of research has been that of during a workout nutrition, combinations of carbohydrate and amino acids or carbohydrate and protein during training maintains insulin at a higher level, cortisol at a lower level, and decreases protein breakdown. If you do that, do you need post-workout nutrients? If you consume a small carbohydrate-protein drink immediately before training, do you need the post-workout nutrients?

At this point there are more questions than answers although I deal with the topic of around workout nutrition in The Protein Book for about 35 pages.

One very interesting study did actually set out to shed some light on this. Cribb down in Australia recruited trained bodybuilders, put them on the same training program and had them consume a whey/dextrose/creatine drink either immediately before and after training or at two times of the day that weren't around training.

So it looked at the issue very practically in that both groups consumed the extra nutrients but only one took it directly around training while the other didn't. The pre/post group showed better lean mass gains and even a slight fat loss.

So I have to conclude that, even if the athlete has been fed, there is still some benefit to putting some amount of the day's nutrients around training. There are other good physiological reasons (e.g. hormonal, blood flow, etc.) that support this idea as well.

Q. How are someone's protein needs affected by dieting? Does someone who wants to lose fat need extra protein? Or is it just for people wanting more muscle?

A. It's been known for at least 40 years that one of the primary factors affecting how well or poorly the body uses dietary protein is calorie intake. As caloric intake goes down, protein retention by the body goes down as well; as caloric intake goes up, protein retention goes up.

Tangentially, while it was usually thought that dietary carbohydrate had a greater impact than dietary fat, recent research suggests that dietary fat intake is as good and could be better from the standpoint of nitrogen retention.

In any case, what this means is that protein requirements go up while dieting. Of course, bodybuilders knew this for years but research has clearly shown that increasing protein intake on a diet has a number of benefits including increased fullness, maintenance of thermogenesis, better blood glucose control and, of course, better maintenance of lean body mass (which also means greater fat loss).

Quite in fact, I'd say that protein requirements will be higher while dieting than while bulking for this reason. When you're eating plenty of calories, the body will use protein more effectively. When you reduce calories, some of your dietary protein will be used for energy by the body, increasing intake to compensate for this is critical to avoiding muscle loss.

Q. The idea of protein cycling for muscle growth seems to crop up every few years. For those readers who don't know what I'm talking about, protein cycling involves zig-zagging your protein intake so that you alternate between high and low levels of dietary protein, with the goal of "tricking" your body into building muscle faster. Is this a worthwhile strategy?

A. I can still remember when this idea was first presented, I actually wrote a fairly long piece looking at the research where I argued that it was crap and my opinion hasn't changed in the last 10 years.

The basic premise is that, with increasing protein intake, the body will increase the oxidation (burning) of amino acids. Quite in fact, at least one researcher has argued that a high apparent protein requirement in athletes is being driven by a habitually high protein intake (which increases amino acid oxidation). That is, athletes need high protein intakes because they have high protein intakes.

In any case, as the logic goes, by decreasing protein intake drastically, you downregulate these processes, such that when you increase protein intake again, the body will utilize it more effectively.

In a related vein, there's a phenomenon called "catch-up growth" that is often seen with malnutrition whereby kids grow at a faster rate ("catching-up" with their peers) due to some of the adaptations. There is some truth to all of this mind you.

But when I looked into what little research was available, it all fell apart in my opinion. The problem essentially has to do with the lag time between when you change protein intake and how the body adapts. In humans, there is about a 7-9 day time span between when protein intake is increased and the body adapts by up- and down-regulating amino acid oxidation.

The problem is that during that time period, the body loses a massive amount of protein. That is, say you go from your habitual high protein intake and slash protein intake drastically. Your body still has all of these adaptations to the previous high protein intake and until it readapts; during that time period, nitrogen balance is just massively negative.

Now, it works the other way of course, if you go from a very low to a very high protein intake, you see this massive positive nitrogen balance for about 7-9 days until the body adapts.

In my mind, what this will end up doing is basically having you waste 14-18 days to end up where you started. Before you can add any new muscle mass during the period of high nitrogen balance, you have to replace what you lost during the period of very low nitrogen balance. End result: no change.

And while at least one of the proponents of this idea has argued that the downregulation of amino acid oxidation is permanent (allowing you to sustain the high net nitrogen balance), there is zero research to support that contention. And research that basically says it's nonsensical.

Additionally, what is often forgotten in discussions of amino acid oxidation is that the body is only burning off "excess" amino acids. In fact, early research looking at protein requirements for athletes used an increase in amino acid oxidation as the indicator that protein requirements had been met or exceeded. The new protein requirement method I mentioned above is actually using an increase or decrease in amino acid oxidation rates to try and determine maintenance protein requirements.

Which is a long-winded way of saying that amino acid oxidation isn't some inherent evil in the first place, it's not as if the body is oxidizing off the amino acids that it needs to support protein synthesis or what have you, it's only oxidizing off the excess that it doesn't need.

Finally, at least one researcher (DJ Millward) has suggested that amino acid oxidation might be part of the body's overall "anabolic drive," with some of the byproducts of amino acid oxidation having regulatory or valuable roles in terms of promoting gains.

As one example, readers may remember a brief fascination of the supplement companies with keto-isocaproate (KIC) and beta-hydroxy-methyl-butyrate (HMB). Well, in the body, when leucine is oxidized, it produces KIC and then HMB.

If Millward is correct and amino acid oxidation actually has a stimulatory role on protein synthesis, this might explain the disconnect between some of the research suggesting that there is a limit in terms of how much protein is required to maximally stimulate protein synthesis and what athletes have found to be most effective. Perhaps the increased amino acid oxidation from the supposedly "excessive" protein intake is having a regulatory effect above and beyond what you'd expect.

Q. When it comes to supplements, the conventional wisdom is that you should take a "fast" protein (e.g. whey) after exercise and a "slow" protein (e.g. casein) before you go to bed. What do you think?

A. Well, there is certainly a good logic to taking a slowly digesting protein, which could be casein, or just whole food, or even whey combined with carbohydrate, fat, and/or fiber at bedtime from the idea of maintaining nutrient availability to support growth, recovery, etc.

I'd qualify that by stating that no research has examined the impact on anything mind you, and there was some weird stuff some years back suggesting that around the clock feeding might be negative (I'd note that this was done in a hospital setting on sick folks) with the idea that the gut needed "rest" from the process of digesting and assimilating food.

As well, some of the intermittent fasting groups have been arguing that there is something good that happens when the gut isn't having to process food but I'll be honest that I haven't really looked into it in huge detail. With all of that said, the general idea is probably a sound one.

As far as the idea of a fast protein after training, I think it gets a bit more complicated. Now, I'll say that there is no doubt in my mind that a fast protein before or during a workout is superior. This is basically a practicality thing, you don't want slowly digesting protein sitting in your gut while you're training unless you like seeing and/or tasting it again.

But there is some emerging research, and some theoretical speculation, that a slow or a mixed fast/slow protein following training will actually yield superior results.

For example, casein (a slow protein) has been found to be superior to soy protein (a fast protein) and some work out of Stuart Phillips' lab suggets that a 50/50 whey/casein mix might be superior. Other recent research has found that milk generates a nice anabolic response following training; interestingly higher fat milk did better than skim milk although the dietary fat would be expected to slow the rate of digestion.

I'm personally a big fan of milk protein isolate (MPI) which contains 80% casein and 20% whey (the same proportion as found in milk itself); although it hasn't been tested in research, I suspect that it will outperform faster proteins in terms of maximizing the anabolic response.

Of course, athletes have long simply consumed a whole food meal following training and this seems to work just as effectively assuming they are hungry enough to eat (training blunts appetite for lot of people which makes liquids superior).

At this point my feeling is that a fast protein pre- and/or during-training with a slow or mixed fast/slow protein after a workout is superior. I would note that I definitely see absolutely no reason for the current popularity of protein hydrolysates (predigested proteins). Not only are they more expensive, but they tend to be bitter tasting; most importantly, research has failed to show any significant difference in digestion speed for whey versus its hydrolysate or casein versus its hydrolysate.

Q. Thanks for the interview Lyle!

Books by Lyle McDonald

The Rapid Fat Loss Handbook
Maybe you need to drop weight fast for a special event, like a class reunion or a wedding. Perhaps you want to look good in a bathing suit and didn't start your diet and exercise program early enough... or you might just want to get your diet over as quickly as possible. If so, the Rapid Fat Loss Handbook will reveal the fastest, most effective way to shed both weight and fat in the shortest time possible.

The Protein Book covers everything you need to know about protein and muscle growth, fat loss and athletic performance. Referencing over 500 scientific studies, the book is the ultimate reference on all aspects of optimal protein nutrition for anyone who's serious about building a better body.

The Ultimate Diet 2.0 (UD2)
The UD2 is possibly the most comprehensive and complete guide to losing stubborn body fat ever written. Inside, you'll discover the secrets of calorie partitioning, how to control where the calories go when you overeat, and where they come from when you diet... the hidden metabolic advantages that elite athletes have, and how to duplicate them to improve your results... why stubborn fat is so stubborn and how to get rid of it... how muscle grows and why so many different training systems can all be right... and much, much more!

A Guide to Flexible Dieting
A Guide to Flexible Dieting reveals how being less strict with your diet can actually make it work better. You'll discover how deliberately breaking your diet (in a controlled fashion) can make it work better in the long run. Free meals, structured re-feeds and even a full diet break are all discussed and explained in detail.

The Ketogenic Diet
The Ketogenic Diet is the first and only book to examine in-depth the scientific evidence regarding low-carbohydrate and ketogenic diets. At 325 pages and containing over 600 scientific references, this will be your complete reference for ketogenic diets. It's unlike any other book on low-carbohydrate diets that you have ever read or seen.

Bromocriptine: An Old Drug with New Uses
The problem of getting very lean or simply losing fat and keeping it off is not a new one. New research is finally explaining the reasons and physiology behind dieting failure and it turns out that many of the problems are in your brain. Bromocriptine: An Old Drug with New Uses explains the physiological reasons behind dieting failures, along with discussing a potential fix: a very old drug called Bromocriptine.