WordNet sense 1 (small in quantity):

slender

WordNet sense 2 (limited or below average in number or quantity or magnitude or extent):

little, small

WordNet sense 3 (being of delicate or slender build):

slight, svelte

WordNet sense 4 (lacking excess flesh):

thin

WordNet sense 5 (take off weight):

reduce, slenderize, lose weight, melt off, slim down