How Often Should You Eat, Part 3: Muscle Mass

More at: http://preliminaryhealthcare.blogspot.com/2014/12/how-often-should-you-eat-part-3-muscle.html

Because of the complex nature of this topic, I’ve broken it down into 5 parts: the first installment is meant to raise your suspicions about traditional advice; here we’ll focus on the effect of eating frequency on muscle mass. The previous post dealt with fat loss, and later posts are on muscle mass and health & longevity. The final installment will discuss how to create a metabolism capable of “Infrequent Eating.”

You may be familiar with protein as a nutrient in foods like meat and eggs. Besides that, nearly everything you think of as your body (hair, skin, organs, muscles, etc.) is made from specific types of proteins; hair protein is different than skin protein is different than the types of protein in your muscles. Proteins are made from smaller building blocks called “amino acids,” which are linked together; there are about 20 important amino acids—depending on the specific order in which they are linked, they create the various types of proteins which compose your body.

When you eat protein, the digestion process breaks it down into amino acids. Once it’s absorbed into the cells of your body, they use the individual amino acids to create the types of proteins they need. As these cellular proteins wear out, they’re targeted for destruction and broken back down into amino acids; some are lost, but most of them are reused as that cell sees fit.

Regarding muscle-cell proteins, wearing out is an inevitable process, but is accelerated by physical activity and inflammation. This is not to be confused with the destruction of these proteins; whereas wear-and-tear is a passive process over which the cell does not control, the destruction of those proteins requires active participation by the cell. Realize this destruction targets the most damaged and dysfunctional proteins, which is necessary to ensure the cell remains healthy and can become stronger by replacing the damaged proteins with (possibly more) fully-functional proteins. The primary stimuli for this destruction are the presence of damaged proteins, extended periods of muscular contraction, inflammation, and the simple absence of “growth stimuli”—growth stimuli are the things which cause your muscle cells to (re-)build proteins:

Mechanical stimulation, as in exercise:
Consider, for example, weight lifting. As your muscles work to move the weight, they experience a proportional amount of tension. That tension simultaneously accelerates the wear-down of the working muscle cells and signals them to rebuild.

Nutrient stimulation:
Here, we’ll only concern ourselves with the “macronutrients,” carbohydrate, fat, and protein. Though “nutrients” tend to make us think of the nutrients in food, realize it can also refer to nutrients we have stored within our bodies: carbohydrate can be stored as “glycogen” within your liver and muscle cells; fat as “triglyceride” within fat cells, muscle cells, and liver; some free amino acids are stored within your liver and muscle cells, though most amino acids within muscle are joined together as proteins. Muscle cells are prevented from rebuilding when they are depleted of nutrients; conversely, rebuilding is allowed when adequate nutrients are contained within a muscle cell. Further, amino acids (specifically, a single amino acid called “leucine”) stimulates the rebuilding process.

During exercise, muscular stores of glycogen and triglycerides are expended as energy, thus inhibiting muscular rebuilding as long as exercise is occurring; at the same time, however, glycogen and fat stored elsewhere in your body (liver and fat cells) are broken down at the command of several exercise-induced hormones (we’ll discuss these hormones shortly), and shuttled into those working muscle cells. In this sense, depletion of these nutrients is disfavored and repletion favored. Similarly, amino acids (including leucine) can also be burned as energy in muscle cells; there are some “free” amino acids within the cell, which are increased by the breakdown of muscle proteins (as addressed above). Furthermore, your liver also releases amino acids (including leucine) in response to exercise. In order to absorb leucine, though, your muscle cells must exchange a different amino acid called “glutamine.”

Glutamine is a byproduct of fuel burning within your cells; as such, its level increases with physical activity. Once created, much of it is removed from the muscle cell and shuttled to the liver (those familiar with this biochemistry will realize I’m presenting a simplified version of this process) where it can be converted into glucose—which can be released back into the blood to provide energy for working muscles. That glutamine which is not removed accumulates within the muscle cell, facilitating the entry of leucine…which is important for muscle building.

Notice the function of leucine changes depending on the context of exercise. It is used as fuel during exercise (thus also contributing to glutamine production, which allows more leucine to be absorbed into the muscle cell), but is a growth signal after exercise is complete.

Hormonal stimulation:
So we’ve just seen that leucine has dual functions, providing fuel during exercise and a growth stimulus afterwards. There are several hormones which function similarly, initially providing fuel to working muscles (hormones are not burned as fuel, but rather make fuel available to muscle cells), then facilitating growth once the exercise has ended; these are the “exercise-induced hormones” mentioned earlier, and include adrenaline, growth hormone, and testosterone. There are also some exercise-induced hormones which only facilitate growth without previously assisting in making fuel available, such as IGF-1. (Don’t worry about the names of these hormones.) It should be noted that these hormones are NOT necessary for muscular growth, but rather assist.

There is another “growth-promoting hormone” that is not induced, but rather prevented, with exercise called “insulin.” Insulin doesn’t increase until you eat something containing protein and/or carbohydrate. Understand that the “growth promoting” effects of insulin are not due to increased building, but rather decreased destruction of proteins.

Frequent Eating and Muscle Mass

The reason Frequent Eating (FE) is promoted for muscle mass is because each meal causes a seeming muscle-building stimulus—the effects of insulin and protein. On the surface, this does make sense. But let’s dig a little deeper.

First of all, we must understand that muscle cells primarily adapt to the mechanical stimulus imposed on them from physical activity. Hormones, as mentioned already, are contributory and nutrients are permissive. Again, hormones are NOT necessary for muscular growth—and apparently neither is abundant nutrition as even food-deprived animals can exhibit unimpeded muscular growth with adequate mechanical stimuli.

Next, let’s understand how these feeding studies are conducted; in a single phrase: “short term.” After the feeding, measurements are taken for protein building and protein breakdown. Indeed, building increases and breakdown decreases. However, it’s premature to assume that this temporary condition necessarily leads to bigger muscles. For example, consider the following contradictory observation: animals subjected to a lifetime of Infrequent Eating (IE), or eating less than their eat-as-much-as-and-whenever-you-want peers have more muscle mass! You see, if your were a muscle-building researcher, working with short-term experiments, you’d conclude eating more causes bigger muscles—but if you were a longevity researcher, you’d conclude eating less (frequency or amount) would lead to bigger muscles! How can that possibly be?

One way to justify this disconnect would be if there is some compensatory mechanism which occurs after the growth-promoting effects of eating, that causes an equal increase in destruction of protein. Indeed, the building phase is self-limited (partly) because it also causes inflammation…which halts building and initiates wear-down and destruction. But further realize that the frequent insulin release of FE inhibits the vital destruction of damaged proteins, which is necessary for the (re-)building of functional proteins. Conversely, IE (eating once a day) allows this necessary destructive process to contribute to the next phase of building.

It’s a mistake to assume that FE is necessary for muscular growth. While it is true that FE induces frequent increases in building and suppresses breakdown, it must be understood that the breakdown phase contributes to a healthy and robust building phase.

Thanks so much for reading. Be well,
Nicklaus Millican