How easy will it be for me to lose weight?

I have had depression since the end of December which was 5 months ago and in that time I've not functioned at all - I don't really leave my house, I don't do any exercise or walking (I lie in bed literally all day). Before I went to the gym, walked home from school etc. and kind of naturally had a slim body which required very little maintenance. But now since I haven't done any exercise or even had any mobility at all for 5 months, when I eat I don't use my energy up so it goes to straight to fat. My waist line has increased and my legs (especially my thighs) have become rather pudgy. If I begin to walk and cycle a bit more and eat a bit healthier will this extra weight be easy to lose? since naturally I am on the slim side or will it be difficult? Any help, advice, personal experiences etc. would be highly appreciated. Thank you.