Previous studies have shown that people with obesity display large differences in risk factors for type 2 diabetes. These results have given rise to the theory about “metabolically healthy obesity”. A new study led by Carsten Daub, Karolinska Institutet/SciLifeLab, Mikael Ryden, Karolinska Institutet and Peter Arnér, Karolinska Institutet, now shows that this kind of “harmless” adipose tissue probably does not exist. The results were published in Cell Reports.