Yoga is practiced by about 15 million people in the United States, for reasons almost as numerous  from the physical benefits mapped in brain scans to the less tangible rewards that New Age journals call spiritual centering. Religion, for the most part, has nothing to do with it.

But a group of Indian-Americans has ignited a surprisingly fierce debate in the gentle world of yoga by mounting a campaign to acquaint Westerners with the faith that it says underlies every single yoga style followed in gyms, ashrams and spas: Hinduism.

The campaign, labeled “Take Back Yoga,” does not ask yoga devotees to become Hindu, or instructors to teach more about Hinduism. The small but increasingly influential group behind it, the Hindu American Foundation, suggests only that people become more aware of yoga’s debt to the faith’s ancient traditions.

That suggestion, modest though it may seem, has drawn a flurry of strong reactions from figures far apart on the religious spectrum. Dr. Deepak Chopra, the New Age writer, has dismissed the campaign as a jumble of faulty history and Hindu nationalism. R. Albert Mohler Jr., president of the Southern Baptist Theological Seminary, has said he agrees that yoga is Hindu  and cited that as evidence that the practice imperiled the souls of Christians who engage in it.