In order to understand how tissues, including both adipose (fat) and muscular tissues, grow, one must understand how the mTORC1 pathway, the central hub of metabolism, functions. The mechanistic target of rapamycin complex 1 (mTORC1) is a multi-protein structure that controls the proliferation and activation of virtually all molecules in the body, via processes such as lysosomal biogenesis, ribosomal biogenesis, autophagy (catabolism or cell death), etc. Simply put, the more the mTORC1 pathway is stimulated, and the more there is tissue growth.
There are five factors that activate the mTORC1 pathway:
-availability of cellular energy (ATP);
-availability of growth factors such as insulin and insulin-like growth factor 1 (igf-1)
-availability of essential branched chain amino acids (BCAAs), especially leucine (found mostly in dairy and high protein food products)
-availability of another amino acid, glutamine, which works synergistically with leucine by acting as a 'gatekeeper' that ensures mTORC1 pathway leucine uptake (also found in dairy)
-availability of satured fatty acids, especially palmitic acid (found mainly in certain oils and cake pastries).
If one wants to limit or maximize mTORC1 stimulation, for example to lose weight or gain muscle mass, then these factors must be controlled. This is mainly done through careful dieting, by controlling caloric intake, but also by controlling food choices as well. The saying 'calories in, calories out' is not entirely true, since different nutrients have a distinct impact on the human metabolism.
For example, milk is probably the most mTORC1 stimulating food that exists, since it is highly insulinogenic (since it's digested quickly), meaning that it causes the pancreas to secrete a lot of insulin and is therefore transported to the metabolic pathway at a relatively fast rate, and it is also rich in leucine and glutamine. Furthermore, it has been shown that, in pregnant women, regular milk consumption causes the transfer of biologically active exosomal messenger RNAs, which increases the mTORC1 pathway's overall effectiveness in offspring. Milk should probably not be consumed by mostly sedentary people, and should only be used by athletes and breastfed babies.
Inversely, meat/animal protein is less insulinogenic than dairy protein, and contains less leucine and glutamine. Meat/animal protein should therefore be favored if one's goal is to lose weight, and vice versa.
Source: not a source, but I study Biochemistry and Pharmacology in Canada.
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Originally Posted by Brett N
