Two sisters whose life sentences in Mississippi were dropped on the condition one donates a kidney to the other must lose a combined 160lb (73kg) before the transplant, doctors say.
Jamie and Gladys Scott, who had been in jail for 16 years, were freed on 7 January because Jamie suffers from kidney failure.
They were convicted in 1994 for a robbery that netted a mere $11 (£7).
Doctors are also requiring Gladys to stop smoking cigarettes.
Jamie Scott, 38, told the Associated Press news agency that she must drop 100lb and Gladys, 36, lose 60lb before their doctors will test their compatibility for a transplant.
The sisters work twice per week with a personal trainer and have been taking aerobics classes since their release.
Jamie, who weighs 254lb, said she also hoped to undergo surgery that would help her lose weight in order to get the transplant sooner.
Jamie Scott requires daily dialysis, which was costing the state of Mississippi roughly $200,000 (£129,000) per year, Mississippi Governor Haley Barbour said in January.
Mr Barbour agreed to release the sisters - who were serving life sentences for leading two men into an ambush in Mississippi in 1993 - on the condition that Gladys donated a kidney to her sister within a year.
Gladys, who came up with the idea for the transplant, volunteered to donate her kidney to her sister in her petition for early release.