From the Kay Erdwinn’s Post Teaching Yoga for Round Bodies
Most fat people find it difficlut to draw the legs into a close cross-legged position, although many can do a loose version.
Almost all fat people will need cushions under the knees, and it is unlikely that any will attempt anything more than Sukhasana (the simple cross-legged position) unless they’ve been practicing for a long time. In time the hip joints will open, but fat in the thighs and calves prevent close folding of the legs.
Also, the habitual contracture of fat students’ external hip rotators means that all cross-legged sitting postures will be more challenging for them, on average. You may also notice fat students surreptitiously “adjusting” their belly out of the way of their legs.
When I demonstrate, I call attention to the fact that I need to do this, but it’s probably better for the average-sized teacher to reassure the fat student individually that this is an important thing to do. The only other caveat in this asana is that fat arms weigh more, and therefore the fat person is working harder than the thinner one.