An anti-obesity drug that prevents the body from absorbing up to 30 percent of ingested fat works significantly better than lifestyle changes alone, a new study has found.

Doctors at St. Luke's-Roosevelt Hospital Center in Manhattan have just completed the largest and longest study of a weight-loss medication and believe that the compound - orlistat - could help millions with serious weight problems.

The medication, developed and tested by Hoffman-LaRoche Inc. of Nutley, N.J., is the first of a new class of compounds called lipase inhibitors. The drug blocks an enzyme found only in the gastrointestinal tract and in the pancreas that is involved in breaking down fat.