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Tuesday, March 27, 2012
The Truth About Meal Frequency: Is Intermittent Fasting for You?
Written on March 26, 2012, by Eric Cressey
Today’s guest nutrition blog comes from former Cressey Performance intern Tyler Simmons.
“It’s best to eat 5 – 7 times a day.”
“Eating every three hours fuels your metabolism.”
“If you skip meals, your body goes into ‘starvation mode,’ you gain fat, and burn muscle for energy.”
Chances are that you’ve probably heard something like the above statements if you’ve read anything about diet or exercise in the last ten years. Many of you (myself included) probably spent a lot of time preparing and eating meals, in the hopes of optimizing fat loss and better muscle gain.
What does the data really show about spacing out your meals? When I started researching the topic of meal frequency in 2010, I assumed there was ample scientific evidence to back up these nearly unanimous claims that smaller, more frequent meals were better than larger, less frequent meals. Boy, was I disappointed.
To my surprise, the scientific literature had some different things to say. My research focused on how changing meal frequency impacts two different things: 1) Metabolic Rate and 2) Weight Loss. What I found was compelling evidence that reduced meal frequency, sometimes known as Intermittent Fasting (IF), could actually help me, so I started an experiment.
In the summer of 2010 I was living in Alaska doing construction and labor, as well as doing off-season training for Track and Field (sprinting, jumping, and lifting). For years I had focused on eating every 2-3 hours, but based on my new findings, I decided to limit all my food intake to an 8-hour window, leaving 16 hours of the day as my fasting portion.
Despite doing fasted, hard labor all day, then lifting, sprinting, and playing basketball, I managed to set records on all my lifts at the end of the summer. Not only was I stronger than ever, but I got leaner too.
Here’s pictures from before and after, about 2 months apart:
Getting lean wasn’t even my main goal; the idea that I could be free from eating every three hours without suffering negative side effects was extremely liberating. No longer was I controlled by arbitrary meal times and tupperware meals in a lunch box. During this summer, I developed the ability to go long periods of time (18-24 hours) without food, and not get tired, cranky, our mentally slow down.
So why didn’t I catabolize my muscles, drop my metabolic rate, and end up looking like skinny-fat Richard Simmons (no relation)?
The Science
The idea that eating several smaller meals is better came from a few pieces of information. The first was because of an association between greater meal frequency and reduced body weight in a couple of epidemiological studies, although this only shows a correlation, not causation. Breakfast eaters are more likely to engage in other health activities, such as exercise, which explains the relationship. In the most comprehensive review of relevant studies, the authors state that any epidemiological evidence for increased meal-frequency is extremely weak and “almost certainly represents an artefact” (1).
The second piece is related to the Thermic Effect of Food (TEF), which is the amount of energy needed to digest and process the food you eat. Fortunately, this is dependent on total quantity of food, not on how it’s spaced, making the distinction irrelevant.
So, now we can see that the supposed benefits from increased meal frequency do not hold up to closer inspection, but why would we want to purposefully wait longer in between meals?
Originally, researchers thought Caloric Restriction (CR) was the bee’s knees. Preliminary research showed that CR slows aging, reduces oxidative damage, and reduces insulin and levels. All good, right? Unfortunately, these benefits come with some nasty trade-offs, including reduced metabolic rate, low energy levels, constant hunger, and low libido, pretty much what you would expect from chronically restricting food intake. These were not happy animals.
Recent research has shown that Intermittent Fasting or reduced meal frequency can convey many of the benefits of CR while avoiding the negative side effects. Some of these benefits include:
Favorable changes to blood lipidsReduced blood pressureDecreased markers of inflammationReduction in oxidative stressIncreased Growth Hormone releaseGreater thermogenesis/elevated metabolic rateImproved fat burningImproved appetite controlSome of these effects may be secondary to the reduction of calories due to improved appetite control, or they may be primary effects of IF, the research is not conclusive on this yet.
One of the most interesting findings was that contrary to conventional wisdom, reduced meal frequency actually causes an increase in thermogenesis (metabolic rate), which is mediated through the increase of catecholamines (stress hormones), such as adrenaline and norepinephrine (1,2). Yep, you read that right: instead of slowing your metabolism down, it speeds it up. Catecholamines also help with the liberation of fatty acids from fat cells, making them available to be burned as energy.
That’s the “why” and the “how” for some of the effects of IF. Whatever the mechanism for it, IF seems to be effective for at least some people, myself included. But before you rush off to go start fasting 16 hours a day, here are some tips and caveats.
Important Considerations
Many people ask me if IF is good or bad, but as with most things, it depends. IF is not appropriate in certain situations. It can be good or bad, depending on who you are (your current health status/lifestyle) and what your goals are. IF is a stressor on the body; one of the primary effects is an increase in stress hormones. If you’re lacking sleep, eating low quality foods, stressed out about your job, and excessively exercising then don’t start an IF protocol. It will backfire and you will end up fat and tired!
Only experiment with an IF program if you are getting 8-9 hours of sleep a night, eating a high quality diet, appropriately recovering from exercise, and don’t have too many mental/emotional stressors.
As far as what goals this works for, common sense applies here. IF is generally best for people who are already moderately lean and are trying to get leaner. If you’re trying to put on 30 pounds of mass, don’t start IF. If you’re an athlete with a very heavy training load, don’t try IF.
For those of you who fit the criteria of goals and health status, I suggest experimenting with the 8-hour fed/16-hour fasted periods. Eat quality foods to satiation in your eating window, especially focusing on the post-training period.
Keep in mind that IF is not for everyone, but it can be a powerful tool at certain times. Most importantly, even if IF isn’t for you, remember that you shouldn’t stress out if you miss a meal occasionally!
About the Author
Tyler Simmons is the owner and head Nutrition/Strength & Conditioning Coach at Evolutionary Health Systems. He has his bachelors in Kinesiology with a focus in Exercise Science and Exercise Nutrition from Humboldt State University. A former collegiate athlete, Tyler specializes in designing training and nutrition programs for athletes of all levels, as well as general population. Learn more at EvolutionaryHealthSystems.com.
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References
1. Bellisle, F., & McDevitt, R. (1997). Meal frequency and energy balance. British Journal of Nutrition, 77, 57-70.
2. Mansell, P., & Fellows, I. (1990). Enhanced thermogenic response to epinephrine after 48-h starvation in humans. The American Journal of Physiology, 258, 87-93.
3. Staten, M., Matthews, D., & Cryer, P. (1987). Physiological increments in epinephrine stimulate metabolic rate in humans. American Journal of Physiology, Endocrinology, and Metabolism, 253, 322-330.
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