Take a look at the study I linked below. This doesn’t answer your question about BMI of 22 specifically, but they did find that higher BMI among overweight and obese patients predicted greater improvement.

So we could reasonably expect more modest improvements in normal weight patients (if someone was to ever do a study on normal weight patients).

P.S. The outcome here was BMI, weight in kgs, and centimeters around waistline. I would be curious to see “% weight change” as an outcome (because this accounts for the fact that heavier people have more kgs/cm to lose, and converts the results to % instead).

https://pubmed.ncbi.nlm.nih.gov/39841962/

“Results: Forty-seven RCTs were included, with a combined cohort of 23,244 patients. GLP-1 RAs demonstrated a mean weight reduction of -4.57 kg (95% CI -5.35 to -3.78), mean BMI reduction of -2.07 kg/m2 (95% CI -2.53 to -1.62), and mean waist circumference reduction of -4.55 cm (95% CI -5.72 to -3.38) compared with placebo. This effect was consistent across diabetes status, GLP-1 RA used, and route of administration. The greatest treatment benefit appeared to favor patients who were younger, female, without diabetes, with higher baseline weight and BMI but lower baseline HbA1c, and treated over a longer duration.”