I have lost 15 and my wife has lost 22 in the last three weeks we did it with 3 miles of walking each day and 10 miles a day on the bikes. not real ones but the bikes at the gym. we also drink 8 glasses of water a day and eat a lot of salad. But it has worked for us like a charm. There is no magic pill or device just sweating a lot LOL.
The walking and riding both use ab muscles so they burn fat and tone the abs.