Extra weight almost always aggravates a bad back. Losing weight almost always HELPS, although doesn’t completely eliminate the pain.
Regarding exercise, no exercise has produced better weight control results than walking. Although people burn many fewer calories per hour than with more vigorous exercise such as running or aerobics, people who walk tend to be much more consistent in their exercise habits. Also, people with back pain should walk for short periods of time but more often throughout the day. For example, instead of walking for 40 minutes at a time, we recommend walking for 10 minutes, 4 times a day. That’s because the benefits to weight loss are the same in either case though 10 minute walks are much less likely to aggravate back pain.