Depending on the nature and condition of your back pain, it is possible to still exercise and lose weight if you have a bad back. Naturally, you will have to modify your form of exercise to prevent further strain and injury to your back. I would suggest a gentle yoga programme will help to strenghten your back and improve flexibility of the spine. A key factor in losing weight is your motivation and desire to lose weight. You need to ask yourself, what do you hope to gain from losing weight? What does your current weight mean to you? How keen, motivated are you to exercise and reduce the amout of foods you eat? What difference would it make to your life if you weighed less? Set yourself small, easy to achieve goals, maybe aim to stretch and walk a bit every day for the next five five days. Take it easy on yourself, be gentle, surround yourself with supportive friends and be patient. Let me know how you get on. I'll be happy to be one of your supportive friends and encourage you to maintain your resolve.