This video attempts to answer the question, what if not just one person but the whole world became vegetarian.
There could be more trees and grasslands to help absorb greenhouse gasses along with less meat factories – animal cruelty.
With less cows raised in those factory farms shown in the Food, INC video there would be less methane which is an even worse greenhouse gas than CO2.
A 5 year study completed in 2010 that concluded eating less meat would help with maintaining a healthy weight.
From the study.
Total meat consumption was positively associated with weight gain in men and women, in normal-weight and overweight subjects, and in smokers and nonsmokers. With adjustment for estimated energy intake, an increase in meat intake of 250 g/d (eg, one steak at approximately 450 kcal) would lead to a 2-kg higher weight gain after 5 y (95% CI: 1.5, 2.7 kg). Positive associations were observed for red meat, poultry, and processed meat.
According to the study if one extra meat portion of 450 calories can cause a little over 4 pound weight gain in 5 years then eating two less meat portion of 450 calories should cause a 4 pound weight loss over the same 5 year period.
So maybe if you eat meat, cut out say two portions a week along with additional healthy eating and lose some weight over time. If you have gained weight it most likely didn’t happen overnight.
The downside to the world going vegetarian is a major change in jobs for all the people who are involved in meat production.