Stress during chondrogenic differentiation of obese and morbidly obese donors has not been assessed before, but our data clearly show an increase in both XBP1 and sXBP1 expression, indicating that obesity‐related stress conditions may also affect chondrogenic differentiation of BM‐MSCs. This evidence concerns the gene XBP1 and obesity due to melanocortin 4 receptor deficiency.