His shape looks like a melon! He is in an urgent need of a diet for medical reasons. He must also have a lot of difficulty reaching his private parts to clean himself. This bun is a good example that overfeeding our pets (and children) is not a gesture of love!
Good points, however, pictures can easily be deceiving. Especially with a rabbit. In my own blog I have pics of my bun in which he looks quite chubby when, in fact, he is not at all.