If you consume an excess of protein, i.e., more protein than you need to build muscle with, you can actually burn more fat (e.g., Forslund et al., 1999). You can also achieve that thick, 'granite-hard' look to your muscles that so many people find to be unattainable when using other eating approaches. By the end of this article, you'll know exactly how to use protein as a fat-burning 'torch' and you'll be well on your way to leaner, harder muscles.
This article was inspired by a question that I recently received: Rob, is it true that it doesn’t really matter what you eat, it’s the total calories? It is more than a case of calories in, calories out. If anything, it is a case of macronutrients in, macronutrients out.
Protein, carbohydrate and fat comprise the three macronutrients in your diet. How many calories you consume of each ultimately determines whether you are getting leaner or fatter at any given moment. (NOTE: If you really want to master the art of macronutrient balance, please read my article "Macronutrient Balance". I promise that it will change the way you look at eating, insofar as building muscle and losing fat are concerned, forever.)
A given amount of calories consumed as, for instance, 60% protein, 20% carbohydrate, and 20% fat a macronutrient profile not at all uncommon for me-can have a fundamentally different effect on body composition than the same number of calories consumed as, say, 30% protein, 60% carbohydrate, and 10% fat. In fact, I can practically guarantee that each of these macronutrient profiles will affect your body composition differently over the long term.
It has been my experience that an excess protein, lower-carbohydrate eating approach works exceptionally well in this regard, particularly in terms of its effects on apparent muscle hardness, or density.
Your Glucose Economy
This has to do with your Glucose Economy, as I call it. The Glucose Economy is my unified theory of dieting. It’s far from proven, but it certainly can explain a lot of things. Glucose is High Man on the Totem Pole of Fuels. Your body deals in multiple currencies of fuel, namely, carbohydrate, fat, and protein. Guess which fuel is your body’s favorite? Carbohydrate -- in particular, glucose (a.k.a. blood sugar). Yes, bodybuilders and non-bodybuilders alike often frown on carbohydrate; your fuel-burning metabolism, however, smiles on this macronutrient. Indeed, glucose is high man on the totem pole of fuels burned, or oxidized, by your body.
The conventional definition of dietary carbohydrate includes sugars, starches and fiber. Sugars and starches are the most common sources of glucose in the diet. They are also the most direct, and therefore, the most metabolically efficient, means of delivering glucose to your body. Starch, after all, consists of chains of glucose molecules linked together. Most dietary sugars (e.g., fructose, maltose) can be converted into glucose, and glucose... well... it already is glucose. What all of this means is that it doesn’t cost your body much energy to turn the sugars and starches so common in today’s foods into glucose.
The See Saw of Your Fuel-Burning Metabolism
Your body’s top metabolic priority in achieving homeostasis is to preserve its overall supply of glucose, i.e., its Glucose Economy. The more carbohydrate you consume, the more glucose you burn. Simultaneously, you burn less in the way of fat. Conversely, the less carbohydrate you consume, the more fat you tend to burn (Flatt et al., 1985). This is your body’s way of trying to preserve its dwindling Glucose Economy for tissues in need. You see, some tissues just can’t do without glucose; for them, there is no substitute. If that’s the case, then how is it that you can survive on a zero-carbohydrate diet? How is it that you can survive without eating (not indefinitely, but for quite some time)? The answer is both protein and fat can be converted (albeit very inefficiently) to glucose.
Let’s consider protein. Protein consists of chains of amino acids. A great many of these amino acids (especially glutamine and alanine) can be converted into glucose. Now let’s look at fat. The most common form of fat you eat (and stored on your body) is triacylglycerol. Each triacylglycerol molecule consists of a glycerol molecule attached to three fatty acids. Glycerol can be converted into glucose. Finally, let’s consider lactic acid. Glucose is stored in your muscles as glycogen. During intense exercise, such as your workouts, muscle glycogen is broken down to form lactic acid. In fact, your muscles and other tissues release lactic acid all day long. It’s just that it accumulates during intense exercise, because it is being produced so quickly. Like glycerol, lactic acid can be converted into glucose. (NOTE: As you can see, the claim made by your high school biology teacher that your muscles can’t ’share’ their glucose with other tissues isn’t exactly true.)
Gluconeogenesis: Making glucose from scratch
So, you see, no diet is truly carbohydrate free. If you are eating food, then you are eating macronutrients capable of being converted into glucose, your body’s favorite fuel, and a carbohydrate if there ever was one. If you aren’t eating food, then your body can turn amino acids (supplied by the breakdown of tissue proteins), glycerol (supplied by the breakdown of body fat), and lactic acid (released from muscle and other tissues) into glucose. The process by which amino acids, glycerol and lactic acid are converted into glucose is termed gluconeogenesis. Gluconeogenesis occurs in the liver, as well as in the kidneys. It goes on all day long, even when you are well fed (Jungas et al., 1992). Gluconeogenesis involves work -chemical work-- and work consumes energy. Guess what? The energy required to drive gluconeogenesis is supplied by the burning of fat; that is, these two processes go hand-in-hand (Jungas et al., 1992; Morand et al., 1993).
Sometimes waste is a good thing: Excess-protein dietsAll of which brings us to the body building benefits of an excess-protein, lower-carbohydrate eating approach. Only a relatively small amount (e.g., 6-15 g) of amino acids is required to stimulate muscle protein synthesis, whether at rest or after your workouts (e.g., Børsheim et al., 2002; Paddon-Jones et al., 2003). Furthermore, some researchers provide compelling evidence that a sustained elevation in blood amino acid levels may not maintain muscle protein synthesis for longer than 120 minutes (Paddon-Jones et al., 2003. So why consume more protein than the small amount you require for building muscle? Why not just consume the additional calories you require as carbohydrate -the most direct form of glucose available?
One of the key reasons is that eating an excess of protein can, when coupled with a reduced intake of carbohydrate (i.e., sugars and starch), reward you with a powerful fat-burning advantage. This anti-conventional eating approach makes your metabolism work for its glucose.