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Wednesday, September 12, 2007

Carbs: Brain Food or the Devil in Disguise?

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Big Fat Disclaimer

I'm not a doctor, nor do I play one on TV. The purpose of this article, or any others on this site, is to condense and deliver information that is "out there" so that you can make your own decisions regarding your health. Consult your doctor before making any major changes to your diet.

The Debate Rages On

The great carb debate has been rekindled with a study released by researchers at Harvard Medical School suggesting that low carb diets may be more effective than a low fat approach to dieting for some people. Studies are published all the time that seem to contradict previous studies and this one was no exception. So what makes this study different from the rest? This study wasn't done at Po Dunk U., my alma mater, it was conducted at one of the most prestigious research universities in the world and it's causing quite a stir.

For 30 years, a low fat approach to dieting has been shouted from mountaintops by doctors, researchers, and dietitians. One can't walk into a grocery store without being lambasted by low fat versions of every food imaginable. And the result of 30 years of low fat gospel? Obesity rates have almost tripled from 13% to 32% of the population. Coincidence? Possibly, but researchers willing to buck the low fat doctrine, and risk being labeled quacks, are conducting studies that suggest there may be a relationship between a lack of exercise, consumption of large amounts of carbohydrates, and obesity.

Insulin - the Gatekeeper Hormone

Here is a quick, and I do mean quick, primer on how energy is stored in your body, as I understand it...and that isn't very well. When you eat a meal and digestion has occurred, the nutrients from the meal end up in your bloodstream to be distributed throughout your body. Carbohydrates end up as glucose molecules, proteins are broken down into amino acids and fats are turned into smaller, triglyceride molecules. The food is broken up into these smaller, base molecules that your body uses for fuel and to repair itself. This post deals with one class of nutrients, carbohydrates, and the base molecules, glucose, that end up in the blood as a result of consuming carbohydrates.

Upon eating carbohydrates, glucose floods into the bloodstream to be stored as a fuel. Your body does this by releasing insulin, a hormone, in response to consuming carbohydrates, and to a lesser extent proteins. The insulin then begins to do its job, signaling the cells in your body to "open up" and absorb the blood glucose as glycogen, but your body only has limited storage for glycogen in muscle tissue and in the liver. Once this amount is exceeded, insulin causes any excess carbohydrates to be stored as body fat.

Here's an analogy for the totally confused. Your muscles and liver are like a sponge that soak up carbohydrates, in the form of glycogen. Your muscles and liver can only store a certain amount of carbohydrates and once that limit is reached, excess carbohydrates are stored as body fat. People who exercise frequently and intensely, in effect, "squeeze the sponge" by using stored carbohydrates, and thus can consume more carbs without storing them as body fat. People who do not exercise, always have a "soaked sponge" and any excess carbs, which will be most carbs, are stored as fat.

The Difference Between Good and Bad Carbs

Another notable quirk of the insulin release system is that our bodies get "tricked" by highly processed carbohydrates, like sugar, white flour and white rice. These foods cause an enormous release of insulin that exceeds the supply of glucose. When the glucose has been processed, lots of insulin is still left in the bloodstream...it's all dressed up with no place to go. The result is the associated sugar crash and ravenous hunger. Our bodies just want to get back into hormonal equilibrium and this excess insulin signals the brain to eat more as a result.

While I think that the Atkins diet is far too carb restrictive, Dr. Atkins did acknowledge that some carbs were of a higher quality than others. The difference between high quality and low quality carbs is in the amount of fiber they contain. His concept of "net carbs" gives credit to carbs that contain a high quantity of fiber. Good carbs have lots of healthy fiber to slow digestion and mute the body's insulin response. Bad carbs like sugar, white flour, and white rice, contain no fiber and confuse the body's insulin release system.

So, how many carbs should I be consuming?

Well, you won't get a specific number from me, but I think that in time the recommendation will be to determine the amount of carbs that you consume based on your level of activity and level of body fat. Your activity level plays a big part in how many carbs you can consume by being the primary mechanism for burning many carbs in the body. Body fat is a very hormonally active substance and seems to have an effect on the body's insulin sensitivity, more body fat seems to be correlated with a higher level of insulin resistance. Another determining factor may be genetics. Approximately 30-40% of people seem to do much better on low carb diets than low fat diets, but the reason for this is yet unknown.

You should eat enough carbs, but the kicker is that you shouldn't eat too many and that amount is tough to determine. There doesn't appear to be an easy, cut-and-dried answer that applies to every person.

More active
Less body fat

Less active
More body fat
<------------------- ------------------------------------------------------------------------------
------------------->
More carbs are OK

Fewer carbs are OK

The spectrum of carb consumption will vary widely from someone who is morbidly obese and gets no daily activity to endurance athletes who burn through carbs with almost no regard to amount. The more active you are and the less excess body fat that you are storing, the more carbs you can consume without storing them as body fat. The less active you are and the more body fat that you are storing, the fewer carbs that you can consume without storing them as body fat. Wherever you fall on that continuum, most of your carbs should come from high fiber fruits and vegetables. Processed carbs not only cause the insulin surge, along with the associated crash, but they truly are the most nutritionally bankrupt class of foods that we consume. Eliminating them for that reason is reason enough.

As I said before, I'm not an advocate of Atkins-type diets that restrict carbs to incredibly low levels (less than 30g per day). I think that 100g of carbs a day is a low level that can be maintained long term and will provide substantial lower carb benefits. Also, I don't advocate the use of low carb products. Eat healthy, whole foods and you won't over consume carbohydrates and you'll save money by not buying all of those expensive, processed products that contain things no one can pronounce.

Exception to the rule

As always there is an exception to the rule of minimizing processed carbohydrates. Your body is especially primed to shuttle carbohydrates into your muscles and liver, as opposed to storing them as body fat, at two specific times of the day...10:27am and 4:38pm, mountain standard time. Just kidding.

Those times are first thing in the morning and after a workout. After sleep, your body is running low on glycogen because you haven't eaten in 8 hours or so, and glycogen is the fuel that keeps your body working while you sleep. Breakfast replenishes that supply and gets you to a good start each day. Never skip breakfast and it's an especially good time to consume carbohydrates. The other time that you should consume ample carbohydrates is post-workout. The first 30 minutes following a workout is a great time to consume carbs, as your body is primed to accept those carbs and get them into your muscles, instead of on your backside.

Wrap up

Don't think that carbs are evil and that by eliminating them from your diet, you will magically lose tons of weight. The calories in/calories out rule still applies. If you consume more calories than you burn each day, and you do this regularly, no magical nutrient ratios will keep you from gaining weight. You must still maintain a calorie deficit if you expect to lose weight. A lower carb diet may be helpful in reducing hunger and reducing the storage of body fat by controlling insulin.

Have you ever tried a low carb diet? How low carb did you go? What did you think of the results?

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2 comments:

Half Man said...

I tried the South Beach Diet. It made me cranky and irritable. I didn't get past Phase 1. I think more in terms of the food groups found in the food pyramid. My concern about high protein type diets is that as I understand it, Americans already eat more protein than needed and it seems like some of the diets don't discern between fatty and lean proteins. I know one person on one of those diets who ate loads of bacon every morning. I am no expert, but that sounds like a recipe for disaster.

Fit Club Scott said...

Saying that any macronutrient is the cause of obesity is a slippery slope. Fat will give you cardiovascular disease. High protein diets are bad for you kidneys. Now carbs make you fat? What the hell are we supposed to eat? That pretty much covers the spectrum of every food imaginable.

The gist of the post was really to suggest that highly processed carbs are a particularly poor choice, especially if you fall into the inactive, high body fat category, because of their effects on the endocrine system.

Eat a calorie defict and cut down on those processed carbs and you'll be light years ahead of most trying to lose weight.