3 meals a day? Yeah right
Eating three meals a day is great if you want to pack on weight.
What happens is when you eat that huge meal your body releases a rush of insulin to break down the sugars. This rush triggers your body to store fat. Why? Because you go all day or hours and your insulin levels drop so low your body thinks you are starving!
When you eat many smaller meals throughout the day you keep your insulin levels stable. Your body feels no need to store any fat. Your metabolism also keeps burning the entire time, so your system is buring calories. Many people find that the MORE they eat, the more calories they burn. The hotter the fire the more it burns.
You will also prevent yourself from breaking down your hard earned muscle by eating constantly. Tell your little friend to learn what an Anabolic state is and what a Catabolic state is. If you only eat three meals per day your body is spending a lot of time in a Catabolic state.. I like to call it a "cannibal" state.. because your body is actually breaking your muscle down to use it as energy. It is much better to keep your body in an Anabolic state almost all the time, then you switch it to a Catabolic state during your workout only. This is when you trigger your body to break your muscle down so that you can rebuild it even stronger. This is why it is important to eat a quality protein immediately following a workout, it kicks your body out of catabolism and into an anabolic state.
Some serious body builders will get up at night just to eat something because sleeping for 7 or 8 hours is too long to go without food. Taking a ZMA is supposed to help you not break down your muscle during your sleep but results are debatable.
I would bet that your friend is just stubborn and a know it all, don't bother trying to explain this too him, its above his head. You say hes fit, but I would guess that doesn't have a lot of lean muscle mass, and probably a pretty fatty mid section. His body is storing that fat for him in case there is famine during the winter!