WordNet (r) 3.0 (2006):

underfed
    adj 1: not getting adequate food; "gaunt underfed children";
           "badly undernourished" [syn: ill-fed, underfed,
           undernourished]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "underfed":
   attenuated, bare-handed, beggarly, cadaverous, corpselike,
   emacerated, emaciate, emaciated, empty-handed, famished, haggard,
   half-starved, hollow-eyed, ill off, ill-equipped, ill-furnished,
   ill-provided, impoverished, jejune, marantic, marasmic,
   on short commons, pauperized, peaked, peaky, pinched, poor, puny,
   shorthanded, shriveled, skeletal, starved, starveling, starving,
   tabetic, tabid, undermanned, undernourished, unfed, unprovided,
   unreplenished, unsupplied, wasted, weazeny, withered, wizened,
   wraithlike