People who are emaciated because they lack food have that physique as a product of their lack of wealth privilege. In the west, the opposite is true for the same reason: People who are obese have that physique because fattening foods are cheap.

This is further compounded by the fact that lower income earners not only have less free time generally speaking for physical exercise (indeed, many of the poorest people in North America have no leisure time as they've filled whatever would have been free with second and third jobs), and even in this overworked state still cannot often afford extraneous expenses such as gym membership.

So-called "fat shaming" in the west is especially hurtful for exactly the same reason that an equivalent "thin shaming" would be in Chad or Yemen, because in both cases the person in question is a victim of their circumstances.