This is a question where the answer is yes and no. Is there any evidence to say eating every 2-3 hours helps you lose more fat ... no. Does eating regularly throughout the day help you stay on track and not binge eat ... quite possibly so.
The Traditional 3 Meals & 2 Snacks Approach.
This reason I believe so many dieters out there follow this principle is because, it gives you regular feeding periods throughout the day, meaning that if you do feel slightly hungry between breakfast, lunch and dinner, you know your snacks are there to keep you tided over until the next meal.
This would be my recommendation to a complete beginner starting a new weight loss regime. Its very simple to follow, you spilt 80% of daily calorie allowance over three meals, leaving the 20% remaining for snacks.
Example, 2500 calorie allowance a day,
Breakfast - 650 calories -
Snack - 250 calories -
Lunch - 650 calories -
Snack - 250 calories -
Dinner - 650 calories
Very easy to follow that plan, when starting on a new "diet" it's always best to keep it just that very simple. Trying to over complete a process so early on is unnecessary. Remember you learn to walk before you can run. Once you have mastered how to build a diet around your life, then start to move things around changing calories to suit your favourite meals.
Then your 2500 calorie daily allowance could look like this,
Breakfast - 400 calories -
Snack - 200 calories -
Lunch - 700 calories -
Snack - 300 calories -
Dinner - 900 calories
Still equalling the same amount of calories and the same results, but designed to suit you more.
How long should I keep on the set meal calories?
That all depends on how comfortable you feel about making changes? Are you enjoying eating the way you are? Does it suit your work and social balance? If so then no leave it how it is until your lifestyle changes. Get those eating fundamentals in first such as getting your lean proteins and vegetables into your meals, basics first then step it up.
If you are struggling to keep your dinner to 650 calories, but your rushing in the morning or don't enjoy breakfast, then yes its time to make some changes. Take those 650-morning calories and add them into meals or bring some dessert in if that's your preference. The options to create a calorie allowance and meals fit you are endless, keep trying new things until you find what suits you.
My Views on Meal Timing
Meal timings to me are something I let just fit around my schedule, I work different shifts most days, my free times for getting food in vary from day to day and some days I don't feel like breakfast but fancy extra serving at dinner. My experience levels of eating to a calorie allowance has given me the ability to be able not to let this worry me anymore.
Yes, I'm sure if I could get a meal in 60 minutes before I workout, I would have more energy and be stronger in that session. What happens if I only have a gap of 90 minutes in my day to get my workout done and have clients before? Shall i not exercise for as long and then train on a full stomach no. I would grab a higher carb/ higher sugar snack before heading into a workout and then a post workout shake, using the calories up later in a meal that I can sit down and enjoy.
Eating regularly doesn't speed up your metabolism, let me correct that it doesn't speed it up enough to make it a make a difference in your days eating. Making the body digest food will help burn some calories, but you are only going to eat the same amount of food through the day, so still has to digest the same amount of food overall.
Learn to get the basics done and then see what works best for yourself. As with all my advice, it's about creating a lifestyle habit. You do this and those hard days of starving yourself because you have run out of calories at 4 pm are long over.
You are going to eat for the rest of your time on this planet, make it fit your life; there is no unique miracle process. It's just a calorie balance, when your lifestyle changes then most likely your diet will too.