The main purpose of a lifting belt is not just to support your back. When you perform a compound movement, you often heard the advice of engaging your core.
This is true, but nobody tells you how. If you just flex your abdominal muscles like you are on the beach and 5 girls are about to pass by you, it’s wrong. It’s not the most optimal way to engage your core.
You are supposed to fill your stomach with air and then brace your core. This will allow you to be a lot more stable and stronger overall. The way I think about it is by comparing the body to a soda can, shaken really hard.
What is really going on there? Well, the air from inside is ‘pushing out’, while the ‘walls’ are holding it, creating such a hard surface that is almost impossible to bend. This is what happens in your body if you master this technique.
By wearing a belt you basically help the abdominal muscles and lower back to do their job better. A lifting belt will also prevent the hyperextension of the lower back during a lift and allows you to create more intra-abdominal pressure.
You can find a full tutorial on how to wear a belt in this article.