Slider for controlling body type, seems to work well. More extreme situations might be hard, but anything that is realistic should work fine.

This slider also have minimal effect on generation unless you use high or low weights, but I found -2 to 2 to be sufficient for most use cases. It struggles a lot more with big bodies than skinny ones, and will usually start to distort after around -2. Adding prompts like ¨fat¨ works as a work around. You can also add "skinny" to negative prompt