DREXX made a good point in saying that you need a high calorie day. Since you are not in 'Ketosis', I presume, you can just up your calories just as DREXX stated.
Now, if you want to be 'scientific' about the matter; the true way of upping your thyroids, in my view, is a drastic increase in carbohydrates. This theory has been used in practice by many bodybuilders I know who come off high-doses of cytomel(T3):
For 3 days: (no training AT ALL)
Eat 600 carbs, w/ your daily protein maintainance amount (your weight x .9=amnt. of protein), and some EFA, like Flax, grapeseed and some MCT's.
This seems like, at a first glance, your going to put on weight, but in 3 days the most I would assume you could put on, considering your diet is properly followed, is about 1/2 lb fat maximum.
My2cents
Mr.X