Vegan

Assuming that an overweight person must eat meat is a logical fallacy.

I wasn't assuming that.

You're hyper focusing on one detail and missing the forest for the trees.

Premise 1: The vast majority of people eat meat

Premise 2: The majority of people are overweight

Conclusion: A very large portion of the population can stand to eat less meat.

Add in that some meat (beef) is a lot more caloric than anything green, and the likelihood of an overweight person being a vegan is quite small (which doesn't mean there aren't cases of it).

I'm not trying to shame people for being overweight, I struggled with it for a long time myself, I'm simply pointing out the majority of people can definitely afford - both money and health wise - to eat less meat than they do.