How much weight can y lose in a asana?

Without any time limit, I suppose you could lose hundreds of pounds over 10 or 15 years. (Gaining the weight back, then losing it again.) Otherwise, it depends on your beginning weight, and how well your muscles are toned up. (You can lose more weight with strong muscles than with flabby muscles.)

The safe limit, in any case, is no more than 3 pounds of fat loss per week.