Just as it sounds
I think the same principles of CICO still apply. You could either be subbing that with high quality protein ( like dairy and eggs), whole foods (grains, pulses etc) and lots of veg OR just highly processed foods like fast food and junk food… so the notion ‘less meat’ doesn’t mean much without a comprehensive overview of what other foods you are eating in replacement.
Check out r/shittyveganfoodporn
Weight gain and fat gain or loss is determined by calories. Depending on how lean the meat you eat, fatter meat have more calories therefore you gain fat and leaner meat have less calories and more protein so you gain muscle (if you exercise) so you might lose fat. But still it is determined by calories at the end of the day.
Meat has no impact on fat gain or fat loss per say.
Makes you more anabolic from a amino acid standpoint so I suppose you could argue it makes you leaner as your body is more likely to grow muscle from the exercise side of things.
Meat is healthy. Flat out.