She aims to put on a stone and a half in a year.

Each week Lizzie posts part of her diary describing how she is finding the challenge.

To sponsor Lizzie visit www.justgiving.com/lizziegrimaldi.

Diary entry: 29th December

"One thing I do feel a lot of the time, and for no discernible reason, is angry. I just want to break something or lash out at someone. It does seem to tie in with a monthly cycle but if I have no hormones surging through my veins, how can it?

That's one thing I want. Periods. I know, I remember the downside – the tummy aches and PMT, but it would make me feel so much more normal. I dread to think what the lack of oestrogen is doing to my bones – I can almost feel it leaching out of them.

I do seem to have come up against a bit of a brick wall in terms of hunger/fullness. All the holes have been filled but the mealtimes keep coming. Please tell me it'll get easier. Barrie and Tony are coming for dinner tonight and I know it could be awkward. I just mustn't get into a state. Do the worry work now and do not rise to it – you know how Barry gets when people are coming over and if I am on edge, it makes it worse."