Eating meat does not make you gain weight, but eating unhealthy meat loaded with saturated fat can. Eating lean meat can help you gain muscle! But remember, there is only so much protein your body needs, that range from 0.8 gm per kg to 1.5 gm per kg. So, control your meat consumption. And always remember to balance out your meat consumption with lots of fruits and vegetables.
If you’re vegetarian, then you should know that protein from plant sources may not be enough to build muscle. Mutton (lamb), beef & other red meat can have high amounts of saturated fat. If you’re going to have them, go for lean cuts. Lean cuts of beef are loaded with iron, muscle building protein and is one of the best sources of muscle building creatine!