Jon,
The problem I had for a few months following Tx was a big loss of appetite.

I was off the PEG, but most foods still tasted poorly or lost their taste after a few bites. Also I didn't like the taste of Ensure or Nutren so I tended not to drink enough of it.

The nutritionist had me start keeping a log of what I was actually eating and drinking and found it just wasn't eating enough calories. She calculated my metabolic multiplier as 14 (rounded up), meaning I need to consume 14 calories a day per pound of body weight and wanted me at 170 pound. So, I need to consume ~2400 calories/day.

As my taste gradually improved, so did my appetite, but it took a few months. Try adding some hi calorie items like chocolate, cheese cake, ice cream (anything hi-cal that tastes tolerable) and consider keeping track of your daily caloric intake.