Women prisoners concerned over their expanding waistlines are complaining their jail diet is piling on the pounds so they no longer fit their clothes.
Peterborough Prison is designed to house men and women
Female inmates at Peterborough prison say food is so high in calories even gym workouts cannot fight the flab.
Inmate Sarah Collings, writing in the prison magazine Inside Time, said she had gone up two dress sizes.
"It's virtually impossible to get the weight off and be the average size 16/18," she said.
"Here at HMP Peterborough' prison blue uniforms are no longer available and we're lucky to get charity shop rejects," she added.
"The only clothing catalogue that we have access to is fine in price but you rarely see anything above a size 14/16, so what are the more curvy ladies supposed to wear?"
It is understood other larger ladies have also complained about the diet and called for healthier food.
Collings is an inmate at the privately run mixed prison at Westwood in Peterborough, a category B jail housing over 800 offenders with just under half of them women.
Spokesman for the prison operator Kalyx, Nicholas Hopkins, said healthy options were always available for inmates watching their waistline.