1. Dennis Quaid,
Wyatt Earp (1994)
Years before Christian Bale became the go-to Thin Man (see: The Machinist, Rescue Dawn), Quaid stripped down to 138 pounds to play consumptive Old West gunman Doc Holliday. Last year, he confessed to suffering from ''manorexia'' and over-exercising in the mid-'90s.
2. Matt Damon,
Courage Under Fire (1996)
To play a heroin-addicted soldier in the Gulf War drama, the diminutive actor shed 40 pounds; by Fire's latter half, he's a physical (and mental) shell of his former self. He has admitted ''it was too much...I was a wreck.'' Damon slimmed down again, aided by a nutritionist, for 1999's The Talented Mr. Ripley.
3. Donnie Wahlberg,
The Sixth Sense (1999)
Wahlberg peeled off 40 pounds to play Bruce Willis' tortured ex-patient/killer which was all the more remarkable because the erstwhile New Kid became virtually unrecognizable. The brief but pivotal scene helped him reinvigorate his then-flagging career and he retained it at a more sustainable weight.
4. Tom Hanks,
Cast Away (2000)
He shed 30 pounds (and gained one Oscar) to play an AIDS patient in Philadelphia; seven years later, Cast Away director Robert Zemeckis halted production on this marooned-man adventure for a year so his 225-lb. lead could whittle his frame to 170 for verisimilitude. Hanks' secret? French fry deprivation.