https://youtu.be/wboZk-Wxsek
How fast should you lose weight? Here’s a quick new video on the basics. For those interested, I’ll link several scholarly articles related to the topic below. ***It’s also worth noting that this is the short explanation for those of you with short attention spans 
???? Metabolism is more complicated than JUST muscle mass, but muscle is a major determining factor. Check it out! Hope it helps!
Sources, summaries and interesting related material:
Very low calorie dieting decreases RMR (resting metabolic rate), making it difficult for obese people to keep weight off once it’s lost:
https://link.springer.com/
Very low calorie diets combined with A. aerobic exercise and B. resistance training, show that resistance training was favorable for maintenance of RMR and LBM, compared to aerobic training.
http://
Wrestlers who didn’t “cut” maintained their RMR better than those who cut repeatedly:
http://jamanetwork.com/
“Given that fat-free mass (FFM) represents a key determinant of the magnitude of resting metabolic rate (RMR), it follows that a decrease in lean tissue could hinder the progress of weight loss. Therefore, with respect to long-term effectiveness of weight-loss programmes, the loss of fat mass while maintaining FFM and RMR seems desirable.”:
https://link.springer.com/
Weight loss by exercise did not effect RMR in 100+ adults, but weight loss strictly via diet caused a decrease in RMR over a year:
