When I was going through chemo and radiation I lived on 2 scrambled eggs, 2 bottles of Ensure and a half s can of chicken noodle soup every day for 2-3 months. Those were the only things I could swallow that actually tasted ok. As I said, I lost about 23 lbs. but I never felt hungry.
Now that I can eat again I start nearly every morning with two eggs (nothing else except on the weekends), by noonish I have slice of pizza, a sandwich or a hamburger or something (no fries, chips, etc.), mid afternoon I'll have a bagel or a muffin or something else as a pick-me-up and late in the afternoon I'll have a high protein snack (power bar, trail mix, nuts, jerky, etc.) then I go home and have a couple of beers before bedtime. I've been able to totally maintain my new lower weight. I eat more on weekends and still have all my favorites (donuts, pizza, pasta, etc.) in moderation. My weight can swing up to 2 lbs/day depending on what/how I eat (I weigh myself daily now).
IMO the number of times you eat and the timing of those meals has a lot to do with it. You need to eat early enough in the day to burn off the calories. Prior to treatment I'd eat a full breakfast, snack on sweets in the afternoon, eat a big meal at night, pound alcohol then snack right before bedtime. I gained weight. I was watching the morning news one day. Nora O'Donnell said something that I think makes sense; Eat like a king in the morning, a prince in the afternoon and a pauper at night.