At one time Roger was fat and therefore started taking Adipose pills. He lost most of the fat and soon was slim. Yet he still continued on the diet. He was on the pills for two weeks, losing a kilo each day. Every morning while he was on the diet, he was woken up at ten past one in the morning by the burglar alarm going off. He phoned in experts, tried to have the alarm replaced and even phoned Watchdog. No burglar could be found. The Tenth Doctor visited him and asked him about the Adipose diet. Roger explained to him about the alarm and the Doctor noted that Roger's house had a cat flap. Taking his leave, the Doctor advised him to "lay off" the pills for "a week or so."
After Matron Cofelia activated full parthenogenesis the remnants of Roger's fat began to turn into Adipose who then escaped through the cat flap. Following the deactivation of the parthenogenesis, Roger returned to normal. (TV: Partners in Crime)