your metabolism needs to elevate to digest protein, you're looking fo at least 1 gram per lb. of bodyweight each day. Agree on the simple carbs, and limit complex carbs. A bit of fat is advisable too, it'll help the body get over the loss of carbs. If you're losing or gaining, you basically eat the same way. It's the activity level and other things that determine what your body does. Many smaller meals throughout the day are also better than 2-3 larger ones.
I disagree with the "at least" 1 gram/lb. notion. IME, it doesn't need to be that high. I think he'll be fine with 170 grams a day. I would say the floor on this for most people is just over 1/2 gram a day per lb. That's the amount I say is needed "at least". I personally shoot for somewhere around 3/4 gram or slightly higher.
Diet is by far the greatest factor in controlling your body fat percentage. I agree you'll be eating similar food, but the amount of it has more bearing on things than exercise or other factors, typically. Again, just my experience.
Finally, the small meal vs large meal debate: in terms of manipulating metabolism, if that's what you meant by "better", I believe this is a myth. I eat small meals to control hunger & prevent the desire to overeat, but as far as keeping your metabolism "running", spreading your meals out throughout the day as opposed to eating 2-3 times makes no difference.
But again, ask 10 people what they think about this, you'll get 10 different answers, so ymmv.