What happens next?

How to deal with obesity in cockatoos
Change your bird's diet.
Cockatoos need a diet comprised of 65% to 80% pelleted food and 15% to 30% vegetables. Seeds and fruit should be given in moderation only.
Obesity is often caused by a seed-based diet, so invest in high quality pellets designed for cockatoos instead of providing a seed diet. Make sure your bird is actually eating its pellets.