cbcb, it is true that a history of yo-yo dieting, particularly low fat dieting, can result in lean mass being lost. If this is the case for you, then 100 lbs of lean mass could be realistic. Keep in mind that those scales can be off by a few % points, and that factors such as hydration and time of day will influence the reading you get (try stepping on the scale before and aftere a litre of water to test this).

Eating LC, specifically eating sufficient calories and adequate protein, will go a long way to sparing muscle loss. Lifting weights will take that even further. If you're new to lifting you can expect to gain some lean mass rather quickly, as well.

Adding just 10 lbs of lean mass can increase your resting metabolism by close to 500 calories a day - something not unheard of over the course of a year.

HTH
Nat