The rescue on the second floor of the small house on Thursday used scaffolding as a ramp to lower the woman to the ground level, the local Rhondda Cynon Taf council said.
The unidentified 19-year-old remained hospitalized Friday and her medical condition was not released.
Neighbors said her weight had risen as high as 380 kilos (835 pounds).
The U.K. has one of Europe's fattest populations: more than 60 percent of adults and one third of children aged 10-11 are overweight or obese, roughly similar to U.S. statistics.
The woman's name is Georgia Davis.