From the Kay Erdwinn’s Post Teaching Yoga for Round Bodies
The only caveat here is that when fat people place their arms at their sides, their arms are not hanging down perpendicular to the floor. Consequently, when a fat person supports him/herself in this asana, the angle of the arms makes them less efficient in strength for the task.
This may make the asana difficult even if the student otherwise has enough upper body strength to lift his/her body. Of course, the arms don’t lift the body clear of the floor in this asana, so it’s not as serious a problem, but it could still present difficulties.
As for any student, sitting on a cushion will facilitate a straighter spine, just as the arms would have if not for the angle. In addition, if the student has a very large belly, s/he may need to spread the legs.