CMG / ZOJ / WENN 1 / 9
CMG / ZOJ / WENN 1 / 9

Teresa Giudice seems to be having a hard time stomaching her prison sentence.

A friend of the reality-TV star told Us Weekly that Teresa's diet and appetite have changed drastically since she was sentenced to serve 15 months in prison after pleading guilty to several counts of fraud.

RELATED: Joe and Teresa celebrate 15th wedding anniversary before prison

"She's skipping meals and surviving on coffee, a few nibbles and wine," the source said, adding that Teresa is down 11 pounds and has been "shaking from all the caffeine."

RELATED: Teresa, Paris and more reality-TV jailbirds

"She looks frail," the insider continues. "Her family is worried as she continues to obsess about prison and waste away."

RELATED: Joe and Teresa's highs and lows

A mother of four, the "Real Housewives of New Jersey" star is due to report to FCI Danbury in Connecticut in just over six weeks on Jan. 4, 2015. Her husband, Joe, will serve a 41-month term once Teresa is released.