Threads for lifting downturned lip corners? (Photo)

My lip corners are downturned . I went to a doctor for a filler but he recommended using thread for long-term results. I am considering fat graft for my cheeks as I lost so much weight,I asked the doctor if the fat graft will enhance the downturned lips and he said not too much but threads will. Is this really a good solution? Is there any side effects? Which threads are the best?Noting that I am 29 years. I am only worried It won’t give the result I am expecting.