One easy contribution, many posting here could make, is simply to go on a diet.
Overweight people are a drain on valuable resources, especially half the world has insufficient food.
Overweight people cost more to transport
Overweight people put an unfair strain on medical facilities

Inevitably overweight people have a larger carbon footprint than thinner people.

Perhaps in this modern politically correct world overweight people should be fat shamed for squandering the world's resources.