I've written about this before and I'll be cutting and pasting from a previous thread but this should go here as well.

There's a long held belief in the fitness community that eating frequently "boosts your metabolism". Often times analogies are used involving a furnace or a car, and they sound good, but unfortunately they aren't accurate.

When you eat, you expend energy from your body processing/breaking down the food. This energy expenditure is called Thermic Effect of Feeding or Thermic Effect of Food (TEF) and is also sometimes called Diet Induced Thermogensis (DIT).

This energy expense happens every time you eat.
The flaw in logic is this: If I experience a thermic effect every time I eat, then certainly eating more frequently will make this happen more often, and this will result in a greater total thermic effect. (I'll burn more calories).

Wrong.

TEF is based on total caloric intakes and to a lesser extent, macronutrient composition (P/F/CHO require varying amounts of energy to process).

And since I firmly believe that choosing reliable resources is an important part of self-educating, I'm going to provide separate studies and reviews from multiple, reliable and tried-and-true sources.

Steve Troutman occasionally posts on MFP, helping people out by providing great information. His website is www.body-improvements.com and I'd like to specifically direct you here, as his explanation of this is stellar:

http://body-improvements.com/resources/eat/#frequency

To quote Steve:

Quite often we hear clients say something like, “Man! I’m so frustrated. I simply can’t stick to eating 6 meals per day and I know it’s hindering my fat loss. Unfortunately for the individuals who fall victim to this myth, it’s not something that’s supported scientifically.

Steve then goes on to explain things in detail.
I would urge people to read the rest of his articles on his website as well. It is packed with great information.


Martin Berkhan is the originator of the Leangains protocol for Intermittent Fasting (not the first IFer, but probably the most notorious and reliable now) For Martin Berkhan's take on this topic:

http://www.leangains.com/2010/10/top-ten-fasting-myths-debunked.html

See myth #1 specifically.


Lyle McDonald has some great information on it here:
http://www.bodyrecomposition.com/research-review/meal-frequency-and-energy-balance-research-review.html

The take home from Lyle's article, in terms of practicality and application, would probably be this quote, this is Lyle here:


* If eating more frequently makes it easier to control/reduce calories, it will help you to lose weight/fat.
* If eating more frequently makes it harder to control/reduce calories, or makes you eat more, you will gain weight.
* If eating less frequently makes it harder for you to control/reduce calories (because you get hungry and binge), it will hurt your efforts to lose weight/fat.
* If eating less frequently makes it easier for you to control/reduce calories (for any number of reasons), then that will help your efforts to lose weight/fat

Or in other words, personal preference.


Some peer reviewed studies:

http://www.ncbi.nlm.nih.gov/pubmed/9155494
http://www.ncbi.nlm.nih.gov/pubmed/19943985
http://www.ncbi.nlm.nih.gov/pubmed/17483007


And it would be wrong of me to exclude Alan Aragon from this list. Here's a good read:
http://www.leangains.com/2011/04/critique-of-issn-position-stand-on-meal.html

Notably this quote:

"The aspects of metabolism discussed in this section are diet-induced thermogenesis (DIT – also called the thermic effect of food), resting metabolic rate, and protein metabolism. As for DIT, differences between varying meal distributions across several studies are negligible. The same lack of difference was also seen in several studies, including tightly controlled designs involving metabolic chambers to measure resting metabolic rate and total energy expenditure. These data further serve to invalidate the dying cliché of stoking the metabolic fire with frequent small feedings."


In conclusion: Do what works best for you. Strictly from a metabolic standpoint when looking only at expenditure(<-- please note the bold), it's not going to matter how you partition your calories.

LASTLY: Gym performance and preferential aspects of dieting should absolutely be considered. This article is strictly discussing the myth that frequent feeding boosts metabolism.