India, May 3 -- I have a serviceable gym at home, with basic machines, equipment, and weights. But more importantly, I have Jai Rathee, a good trainer who is able to discern the difference between required exercise and undesirable excess.

To have this trained balance is necessary, especially when, across India's metropolitan skylines-and increasingly in smaller towns too-glittering gyms rise where once there were modest parks, akharas, or open maidans. Fitness studios advertise "body transformation" in 45 days. Young men measure protein intake with scientific precision. Young women follow elaborate regimens of calorie deficits, intermittent fasting, and "clean eating." Watches monitor sleep cycles, heartbeats, oxygen levels, and the numb...