Dad uses the family to test his fit-in-four weeks diet book. But as the Pinkers all get fatter, not fitter, can Gran save the day?

It's winter and the Pinkers are out of shape - so Dad decides to use the whole family to test out his ideas for a new fit-in-four weeks diet book. But after a few weeks of early morning runs and cardboard flavoured ready meals, (meaning Peony needs chips and double helpings of pudding at lunch every day to make up) Peony's become so unfit can barely walk up the hill home. And she's supposed to be climbing Mount Snowdon in just a few weeks! Can Gran get the family back on track with some wise words and common sense? Hilarious family comedy with a self-help twist.