We are quoting from  Marathon Statistics 2019 Worldwide (Research). You can view this source for the original data. Note this study was only for recreational runners and elite runners were eliminated from the database to avoid bias

India average marathon time the slowest among nations

The Slowest Nations

The worst performing nation globally is the Philippines (5:25:35) followed by India (5:05:21), and Mexico (4:53:11).

The world's fastest marathon nations

India average marathon time slowest | Growth in marathon running highest

India is at the top when it comes to growth in Marathon Popularity. A lot this seems to be coming from more women taking to the sport across nations. With a low women turnout still, India can grow faster for years to come

India's fast Marathon Growth

marathon growth across nations