This was my guess too, but they later did another study with rats and it did not show significant effects.
https://sciencenordic.com/climate-change-denmark-obesity/four-years-later-is-co2-making-us-fat/1440745
This was my guess too, but they later did another study with rats and it did not show significant effects.
https://sciencenordic.com/climate-change-denmark-obesity/four-years-later-is-co2-making-us-fat/1440745