Obesity has been linked to climate change in many studies. Here's a summary of one typical example:

https://www.marketwatch.com/story/another-reason-to-combat-t...

People in developed countries eating more food than they need is very wasteful, not just in food production, but the extra fuel needed to transport these people, the extra material needed to clothe these people, etc.

Anybody who's overweight or obese can't be credible if they act concerned about climate change and won't do something as simple (and without cost) as eating less food.