I am a 76 year femail who would like to lose about 10lb. I was 11st 1lb and would like to be about 10 1/2 or a bit lower. I am unable to do strenuous exercise due to copd but can manage 1-2 mile walk on the flat. I have lost a couple of pounds this week, but gained a pound on Weds despite keeping within my calorie allowance and being quite active. This is disheartening. How can I prevent the odd gain?