1. Increased risk of suffering from low back pain.
There is a ton of research out there that shows that obesity makes back pain more likely and makes people more likely to seek care for low back pain, including chronic back pain.
2. The components of the spine can wear down.
The spine is strong, but it is also delicate. Vertebrae are supported by soft tissue called discs, tendons, and ligaments. This allows for movement so that you can be MOBILE. However, these tissues are prone to wear and tear. A healthy body will experience wear and tear with age. Now add extra weight and you increase that wear and tear.
3. Extra body weight increases damage to the spine.
Think about this for a minute. You are carrying a heavy box or a couple of bags up and down stairs or across a parking lot. How do you feel after that? It can wear you down. At first you feel fine, but then the longer you go, the more tired you become. Extra weight is something that you carry around with you everywhere. You are constantly putting your body through excessive force and the joints and muscles are having to deal with the extra pressure.
4. Injuries can become more severe.
Extra weight makes every accident and injury more damaging. Slipping or catching yourself in a way that would have been okay before, can now cause muscle tears and tendon ruptures. Every time you are in an accident, your body will have a harder time maintaining safe alignment.