Hey,
I started exercise in week 2 - but it was something i felt i really wanted to do! If you feel like you want to - then give it a go, and if you feel tired then just stop - I drink 1 litre of water during my fitness class and take more breaks than anyone else!!! I just go at a pace that I feel comfortable with.
I guess it depends how long you have not exercised for - maybe just start off walking - or short cycles. What ever floats your boat.... and for toning... wellllll..... have you ever heard of slendertone? Its the whole rage here on this forum... but thats a whole other thread!
I think its a good idea to get out and do something, even if it is a light walk, after all its a win/win/win situation.
WIN - You are out so less tempted to think about food.
WIN - You are building your fitness (even if it is only light)
WIN - You are helping your body to burn a few extra calories
WIN - You are clearing your head and helping yourself to destress
I think exercise can only be a good thing as long as you feel comfortable, you enjoy it and you dont push yourself too much.
Good luck with whatever you decide to do!
xox