“A review is by Miyazaki and Esser provides a thorough, up-to-date discussion of the cellular mechanisms
regulating muscle protein synthesis. Their review focuses primarilyon work performed in animals and in cell culture and highlights several key findings, including the central role of the
mammalian target of rapamycin complex 1 (mTORC1) signalingpathway in regulating muscle protein synthesis.

The authors point out three primary activators of mTORC1 in muscle:
1) growth factors/insulin,

2) amino acids

3) mechanotransduction”

So protein / calories will cover number 1 and 2 and the local stimulus (strength training) will cover #3

Rock on
Mike T Nelson

mTOR can be stimulated by many things.

From Amino acid regulation of TOR complex 1. Avruch J, Long et al “TOR complex 1 (TORC1), an oligomer of the mTOR (mammalian target of rapamycin) protein kinase, …… controls cell growth in all eukaryotes in response to nutrient availability and in metazoans to insulin and growth factors, energy status, and stress conditions.

Weight trainining can stimulate it also as shown in “Effects of chronic overload on muscle hypertrophy and mTOR signaling in young adult and aged rats.” from
Chalé-Rush A et al. 2009

The mTOR1 complex is only ONE item of many many things than can stimulate hypetrophy, but it seems to be very important. Leucine itself seems to have an direct effect on it, but to what degree that results in visible changes in muscle size is up for grabs yet.

Metabolic Flexibility
One can increase their Metabolic Flexibility by exercise for sure. This seems to be the best way by far. I don’t have any direct data on it, but I believe it can be modified by nutrition (some data), lifestyle and mobility. The body has the ability to switch from carbs to fats in a very very short period of time due to eating mixed meals. You can think of theses processes going on at the same time. You can also push it one way or another by shifting the composition of the diet from more carb based to more fat based, although I think this may decrease your Met Flex in a NORMAL athlete. If you are diabetic, you probably don’t NEED more carbs since your body has a hard time processing them (as always, talk to your doc).

Paleo Diet
I think it can work, esp for those that are not very tolerate of carbs. Long term, people seem to do just fine as long as they have essential fats and enough protein. There are a ton of data to show that feeding carbs during long endurance events is ergogenic though (enhance performance).
In a perfect world, I’ve wondered about taking some one to a low carb diet to maximize fat for fuel and then replace their carbs (fill glycogen stores) right before a big race to “trick” the body into burning more fat and still using carbs during the race. Trying to get the best of both worlds. The data I have seen on “fat loading” does not seem to show this though. The downside is that I think it may take someone 4-8 WEEKS to be fully fat adapted as a fuel source.

Rock on
Mike T Nelson

how much in your opinion is needed to increase optimal muscle gain based on calories? is this dependent on bodyweight, or simply whatever weight you want to reach?

metabolic flexibility is rather interesting and have been followed your writings on it for quite a bit of time. it’s interesting to think that our body is able to switch fuel sources quite easily. what ways do you feel one could increase their metabolic flexibility?

also, i’ve been curious on what you think of the paleo diet? although right now carbohydrate based diets seems to be quite rampant (in the form of simple, processed carbohydrates (white bread, white rice, pasta, etc), i’d be curious of any long-term studies conducted with people following a paleo diet where proteins and good fats are the major fuel sources.

Rock on
Mike T Nelson