Research shows that eating every 2-3 hours is one of the most important ways to improve health and body composition. Frequent eating (of well-chosen, properly sized meals) stimulates the metabolism, balances blood sugar, and helps maintain your lean mass while giving yoru body a reason to burn off your extra fat mass.
How many meals per day should you eat?
That's easy: just divide the time you're awake (say 15 hours) by 3. So if you're up for 15 hours a day, you can shoot for about 5 meals a day.
Based on your goals, you may need to eat more or fewer meals than this. For example, if your goal is weight gain and you've got a fast metabolism, you'll likely need to eat more frequently. Some of my clients in this situation eat up to 8 meals per day. And if your goal is to lose weight you may need to eat less frequently. Some of my clients in this situation eat 4 meals per day.
A good rule of thumb for everyone is to start with eating 5 meals per day. You can later make adjustments based on your results and goals.
Rather than thinking of "snacks" vs. "meals," think in terms of eating opportunities. In other words, every time you eat you have the opportunity to make your body worse or better. Sure, some meals may be smaller then others, but most importantly is WHAT you eat and WHEN you eat it.
Time for a snack...or meal?