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Metabolism Myths

I don’t care how many times you’ve heard it: Eating more frequently does not speed up your metabolism.

By
Monica Reinagel, M.S.,L.D./N,
February 18, 2009
Episode #031

The topic for today’s show was inspired by a comment that was posted on Twitter the other day by new media guru Jason van Orden. Jason wrote that he was trying to eat every two and a half or three hours without fail in order to keep his metabolism burning.

The idea that going too long without eating will cause your metabolism to shut down is a very popular notion. As I told Jason, it’s also pretty much hooey.

Now, it’s recently come to my attention that listeners of the Nutrition Diva podcast are using the information in these shows to correct their co-workers, spouses, and even perfect strangers on nutritional matters. All I can say is, “Keep up the good work.” There is a lot of nutrition nonsense in the world. Together, we can make a difference! And this week, you’ve got your work cut out for you.

I’m not sure who first promoted this idea that eating several small meals a day would promote weight loss by stoking your metabolism but it has quickly become dietary dogma. I think one of the reasons that it has become so widely accepted is that people haul out some very scientific-sounding explanations that seem, well, very scientific and, therefore, believable.

There are two basic arguments and we’ll tackle them one at a time:

Going Into "Power-Saving" Mode

The first goes like this: your body, when deprived of food for a period of time, will go into “starvation mode.”   This is when the body burns fewer calories in order to conserve energy, just in case the food shortage continues. During a famine, you’d need to live on your stored fat. Down-regulating your metabolism is a way to make those fat stores go a bit further.

It’s similar to the way your laptop adjusts its energy usage when it’s running on batteries, by making the screen a little dimmer, for example. When food is plentiful again, your metabolism goes back to normal, just the way your screen gets brighter when you plug your laptop back in.

If there were actually a famine, you’d be glad that your body is designed this way. But, if you’re trying to lose weight, the last thing you want is increased fuel efficiency. You want to be burning through stored fat like an Escalade burns through a tank of gas. So, the trick is to reassure your body that there is no shortage of food by eating every few hours. Your body will oblige you by continuing to burn calories with reckless metabolic abandon. Or so the story goes.

It makes sense, doesn’t it? And, it’s sort of true. Your body does respond to a prolonged fast by slowing your metabolism to conserve energy. Here’s the thing, though: your body doesn’t go into starvation mode if you go four hours without food. In fact, it takes about three days of fasting or serious caloric restriction for your body to respond with any sort of metabolic adjustment.

The Cost of Doing Business

The second argument, which sounds even more technical and is, therefore, even more impressive, has to do with something called the thermic effect of food. This is a term that scientists use to describe the energy that your body expends releasing energy from your food.

Think of it as a sort of transaction tax that your body charges you to convert the energy in your food into a form of energy your cells can use. If a meal contains 300 calories worth of food energy, converting that food energy into cellular energy might use up 30 calories or so. So you’d end up with just 270 calories worth of energy when it’s all over. It’s a little like changing money in a foreign country. In order to convert your dollars into euros, you have to pay the money-changer a fee.

Some people have interpreted this to mean that if your body is constantly in the process of digesting food, it will constantly be burning calories (via the thermic effect of food) and that if you go too long between meals, you will be missing out on this calorie-burning opportunity.

Bosh! Just like at the money-changer, the fee to exchange food energy into body energy is simply a percentage of how much you’re changing. It doesn’t matter whether you exchange all your money in one lump sum at the beginning of your trip or change small amounts of money three times a day. The fees will be based on how much money you convert. And the thermic effect of food is based on how much you eat, not when you eat it.

The Bottom Line

There’s nothing wrong with eating six small meals a day instead of the traditional three-square. Some people find this works better for them. For example, you may find that you make better dietary choices if you don’t let yourself get as hungry between meals. But rest assured that going 4—or even 12—hours between meals will have virtually no effect on your metabolism.

It’s also not necessary to eat every few hours in order to keep your blood sugar steady. In fact, spacing your meals out more can have some very beneficial effects on your blood sugar and on other aspects of your health, as well. I’ll talk about these in next week’s show.  In the meantime, if you want a Quick Tip about your body's ability to metabolize food while you sleep, head right on over here.

 
Administrative
 
This is Monica Reinagel with your quick and dirty tips for eating well and feeling fabulous. If you have a nutrition question for me, send an e-mail to nutrition@quickanddirtytips.com.  Or, send me a tweet on Twitter!
 
Have a great day and eat something good for me!
 
RESOURCES: 
 
intakes of energy (Scholarly article in American Journal of Clinical Nutrition)
 
Eating more meals does not increase your metabolism (Good summary of research in lay-friendly terms)

 

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