What are the most effective alternatives for meat?

It has broadly agreed that eating meat is a significant contributor to CH4 emissions (and CH4 is 25 times as potent a greenhouse gas as CO2), released owing to the massive number of cattle grown for meat. But asking the world to stop eating meat is not going to cut it unless alternatives are presented. What could be such effective alternatives to meat, including effective plant-rich diets?

How will it have a positive impact?

Better Health of Planet

Who will it have a positive impact on?

Developed Countries