I recommend you to use lora weight : 0.5 ~ 0.75. If you don't like too chubby style body, then use lora weight under 0.75.
And there exists some trigger words, but you can generate chubby girls with any words to depicts bbw woman.
example : chubby, plump, big breasts, big ass, skindentation, ...
And I used the face lora
: https://civitai.com/models/335829/kim-taehee-korean-actress