Gaining weight. Help!

It's time to debunk the myth that people who are being treated for cancer loose weight and waste away. As with all aspects of this amazing adventure, the opposite is true for me. I have had more appetite than I usually do. I crave food. For the most part I want healthy non processed food. But I also have a sweet tooth, and I want to eat crunchy things.  I have been working out regularly. Im sure that is a reason why Im just hungry all the time. My body seems to want to balance the energy expenditure with my caloric intake. Well, obviously it isn't really balanced. There is more going in than coming out.
 I can no longer wear the cool jeans I got last January when Katie and I did our 'What not to wear' thing at Nordstroms last year. Today I got on the scale and found that I had gained 5 pounds since I started chemo. Altogether I have gained 15 pounds since Mike died. The thought of going on a full out weight loss program is just too much for me with all I have going on.  I just don't know what to do about this. Im hungry a good deal of the time. Normally I would just live with this feeling and make good choices and plan carefully.  It just feels like the brakes are off and Im rolling down a hill faster and faster. 
The doctor says that the prednisone I taken as part of my chemo cocktail can cause this. The prednisone helps prevent some of the side effects from the chemo. But it does make you hungry too. Im going to ask him what to do about this when I see him next week.
Christmas is coming up. We leave tomorrow for Sacramento. We will only be staying for 4 days. That is a good thing. It means that I will only have 4 days to eat Christmas stuff. We return to SD on Monday. On Tuesday I have my next chemo.
As with all aspects of my life, I know the answer to this dilemma is in my head. I just need to figure out how to access it.