Question about metabolizing body fat and building muscle while dieting

If a person is substantially overweight, let’s say 50 lbs, and they go on a strictly vegan diet, and begin exercising and weightlifting - two questions re this scenario:
1: Can carbohydrates be used to build muscle?

2: In the absence of a significant intake of high quality protein (ie lean meats) can body fat be metabolized into building muscle, or does it require that you consume protein in some fashion, whether high or low quality?

There is a certain set of amino acids that we humans can’t synthesize, so we either get them from food or go without. Whether or not those are necessary for muscle building takes second chair to the fact that the body just isn’t going to devote a whole lot of energy to muscle building while it’s in a hypocaloric state.

To a degree, but you can,(and I have) built muscle while dieting. Not amazing amounts, but definite increases in muscle mass. Granted I had a good amount of lean meat protein in this diet, but I was running an approx 1000 calorie per day deficient below weight maintenance levels for the weight I was carrying at the time, and was still able to build muscle.

Yes, you have to consume protein, and you have to consume the right kinds of protein too. If you’re eating meat then you get all the right kinds of protein without really thinking about it (along with fat, cholesterol, growth hormone, minced rectum and whatnot). If you’re not eating meat, you can still get all the right kinds of protein, but you have to pay a little attention to variety (not too difficult, though).

Someone is bound to come along this thread and mention about how amino acids (which make protein) can be made from glucose. In a way this is true, but it has 2 problems, which is 1) it depends on nitrogen, which comes from protein, and 2) not all of the necessary amino acids can be made in this way. So for your purposes, you can consider this fact a bit of interesting trivia that would be more interesting if you ate nothing but corn. (Note: Don’t do that).

Read the above link. Follow the links in it. You’ll learn stuff.

Being on a vegan diet is not the same thing as ‘dieting’. And there are believe it or not vegan body builders although obviously they are eating plenty of greens and vegetables and not pretzles and beer.