If you are a vegetarian and cannot eat red meat than lentils are a great supplement for your muscles. Lentils just like red meat are full of proteins and they can easily fill up your stomach and give nourishment to your body, bones and muscles.
In India lentils are a part of the diet as most Indians do drink dal along chapatti and vegetables. The majority of Indian population is vegetarian and this is the main source of proteins that they get from their meat free diet.
To build muscle you need to consume lots of protein rich diet, beans and meat are the most common ways to get it but these are not only ones. If you get tired of eating the same diet over and over again try lentil rich diet and be a vegetarian for the day.
Off course you will need other vitamins and minerals besides proteins and you can get it from fruits and vegetables, these healthy greens are a full source of healthy vitamin and minerals. A study was done in the UK that shows that you should eat at least 7 different portions of healthy greens a day. Read my early blogpost titled Eat 7 Portions of Fruits and Veg a Day and Beat Cancer – studies at University College London say.
Regarding fitness exercise you should do cardio exercise at least 3 times a day to improve your hearth rate. A good hearth rate is 72 pulses a minute, this is what professional athletes do have. With a good healthy hearth rate you will drastically improve blood circulation which in other words means better transportation of nutrients to the body, bones and muscles.
So to conclude you do not need to consume red meat to gain muscle you can still do it while being a vegetarian and this in my opinion is a better option. Since over consumption of red meat has been proven to be unhealthy for many.