Science has known for years that the fewer calories you ingest, the slower you age. Metabolic processes induce a lot of wear and tear.
As far as reversing aging, the protein thing may have some merit, but I would remain skeptical for now. My 2-cent guess is that truly reversing aging will involve some unholy cocktail recipe of stem cells, genetic manipulation using CRISPR, lots of fasting, and maybe some advanced vaccines (we’re learning vaccines can train the immune system to do all sorts of interesting things beyond fighting infections).