Starting with a few basics: AMPK is the longevity pathway. mTOR is the growth pathway.
mTOR is anabolic, meaning that it’s associated with building and repairing muscles after a workout, with the end goal of having bigger and stronger muscles. mTOR fueled by eating lots of protein, in particular foods high in the amino acid leucine.
AMPK is catabolic. It’s associated with reusing and recycling metabolic resources (i.e., cleaning debris fragments out of our cells and breaking them down into amino acids, which the body then turns into proteins) The body does this when we’re fasting because it doesn’t have any nutrients coming in. AMPK is associated with other beneficial processes such as autophagy and apoptosis.
When AMPK is on, mTOR tends to be off, and vise versa.
Turning AMPK on while turning mTOR off, either by the use of drugs or by dietary manipulation, helps to extend the lifespan in every species ever studied in a laboratory. Some animals live 50 percent longer than control animals of the same species if their mTOR is kept shut off or subdued by restricting calories or protein.
We don’t know for sure if doing so would extend the lifespan in humans, because it would be impossible to do similar studies on humans in a lab. (We’d need to imprison human subjects in a lab setting for decades… longer than a human lifespan… then see how long they lived, to find out… not likely, fortunately!) But extrapolating from the studies that have been done on numerous other species, it’s almost certain that it would.
We do know that we can turn AMPK on and mTOR off in human beings (like other animals) by fasting, eating a lower-protein diet, or eating less leucine (an amino acid found mainly in animal protein).
This does not mean mTOR is bad. We need it on part of the time to build muscle and prevent sarcopenia. If we kept mTOR off full time, we’d waste away and our immune systems would stop working.
The best approach from a longevity POV appears to be switching AMPK on most of the time (by fasting eating low protein, or eating foods low in leucine), and turning mTOR on (by eating high protein meals rich in leucine) only around the time that we’re actively building muscle.