The final entry in the catalogue: those who regulate what they eat, offering their life-energies into the life-force itself as a discipline. And then Krishna wraps up the entire list with a broad embrace — all these practitioners, regardless of which form they practice, are knowers of yajna. Through their yajna, their impurities are destroyed.
The inclusiveness here is striking. Krishna has listed devotional worship, knowledge-seeking, breath control, sense restraint, austerity, charity, study, and dietary discipline — and He calls every practitioner a yajna-knower. There is no single correct method. Sincerity and commitment are what count.