Accumulation of old or modified proteins contributes to aging and can be reversed by fasting or lower levels of branched-chain amino acids.

“Now, why do you want to recycle proteins? You might say, well, who cares about recycling proteins. Well, Alzheimer's disease is a good example of proteins that get modified and accumulate in your brain. And it happens not just in the brain, but in all tissues. We have these old proteins that linger, 'cause us to get old to malfunction, but it's reversible and it's reversible, by fasting, it's reversible also by having lower levels of these branched-chain amino acids, at least part of the week.”