I became a flexitarian because one thing that I noticed whenever I consumed meat was that I felt so heavy. Since I am very careful about what I eat and how much, I did not eat more, but it seemed that I felt fuller. Over time, I also noticed that my weight increased and most of the weight accumulated in form of belly fat. As I transitioned gradually from meat to vegetables, I felt lighter and the fat simply melted away.
While the physicist in me makes me believe that a calorie is a calorie, that is not how the human body sees it. Dr. Anne-Claire Vergnaud concluded that the same amount of calories consumed from meat lead to more weight gain. And what is even surprising is that instead of red meat being the evil, it is poultry that resulted in weight gain.
The conclusion is simple. You do not have to become a vegetarian, unless you choose to, but definitely limiting your meat intake will help. I only eat meat when there is nothing else to eat or I go to a restaurant that serves delicious dishes that happen to be made from meat.