I agree that losing body fat is the number one priority, but I wish the research would focus on that rather than the number on the scale. Losing a bit of lean muscle mass along the way is important for its own sake, and also because it's a confounding variable for what I actually want to know, which is how much fat (not weight) a person lost.
Losing a bit of lean muscle mass along the way is not important compared to the huge health gains of losing the weight.