Wednesday, May 1, 2013

Engineering the Perfect Body, Part 3: Body Weight

With every year that passes in the US, obesity is becoming a bigger problem (pun intended). If you listen to health experts and diet gurus, you might get the impression that this problem is simply a matter of willpower: You have to stop eating all the delicious foods that you see around you and get off your butt more. This is true, but the real problem is much more complicated than that.

Body Weight is Supported by Calories
There is one simple truth when it comes to body weight: Your weight will track your calorie intake.(1) In general, the more you eat, the more you will weigh. The less you eat, the less you weigh. This was demonstrated dramatically during the starvation studies conducted in the 1940s. (2,3)

(Of course, eating too much or eating too little is complicated by the fact that your brain can adjust appetite, hunger, and metabolism based on feedback.)

To explain what I mean, here's a quick recap from my ideal body weight post. Your brain will establish an ideal body weight set point based on a kind of default setting established by your DNA and feedback from your environment (a.k.a., physical activity). Your brain then uses other feedback systems to figure out your current body weight, which ultimately determines how many calories you need to eat on a given day (i.e., how hungry you will be).

Here's another way of putting it:
  • If your brain figures that you are underweight, then it will create a calorie surplus by increasing your appetite and hunger, as well as slowing down your metabolism. This allows your body weight to increase
  • However, if your brain estimates that you are overweight, then it will create a calorie deficit by decreasing appetite and hunger, as well as speeding up your metabolism. This allows your body weight to decrease.

Physical activity also adds to this process:
  • Every calorie that you burn through physical activity--from sitting in a computer chair to running a marathon--is tracked by your brain. So, if you decide to do crazy amounts of cardio in an attempt to "burn" extra stored calories, then you will only succeed in increasing your appetite and hunger as your brain gets back every calorie you expended during your workouts.
  • If your muscles were not strong enough for the exercises you engaged in, then you will build more muscle. Your brain will only keep this muscle so long as you use it. Additional muscle mass can also displace fat mass as your brain tries to keep your body weight at or around your ideal set point. (However, it is possible to elevate your body weight set point with the right amount of heavy/intense exercise, allowing you to maintain a heavier body weight.) 

This relatively simple process is constantly happening every day without any conscious involvement on your part. This system allows you to effortlessly maintain a healthy body weight without calorie-counting, starvation diets, or tricks to "boost" your metabolism, so long as your feedback systems are operating correctly. If your feedback systems are not operating correctly, then you will always struggle (and fail) to maintain a healthy body weight.

It's also easy to understand that if your brain thinks that you are starving, your lowered metabolism will not make you want to exercise (since exercise burns precious calories); conversely, if your brain thinks that you are overweight, your increased metabolism will make you feel like exercising all of the time. In other words: People struggling with their weight may not be overweight because they are lazy; they may be lazy because they are overweight. (4)

Why are Some People Overweight?
So, if each person has this super awesome body weight regulation system, why are some people helplessly overweight?

I've put a lot of thought into this question. My answer is based on my research into the conspicuous lack of overweight and obesity in traditional human populations, (5,6) the sudden explosion of obesity in the US (since the 1980s), and the effortless permanent weight-loss results commonly experienced by those who try a Paleo-like diet. (5)

Although there are a number of good reasons that someone could be overweight (e.g., brain damage, inactivity, infection, dietary toxins, addictive foods), I believe that most people who are overweight are suffering from a malfunctioning body fat/weight feedback system (7) that, ironically, simulates starvation.

The brain can calculate the amount of body fat a person has based on the level of the hormone leptin circulating in the blood. Because leptin is produced by each fat cell, the more body fat you have, the higher your blood leptin level is (and vice versa).

Normally, when leptin levels are too high (meaning there is too much fat weight, making a person too heavy), the brain lowers hunger and appetite and increases metabolism to create a voluntary calorie deficit that will get rid of this extra weight.

If anything interferes with the brain's ability to detect leptin, then it will think that a person has less body fat than they really do. (8) This interference leads the brain to falsely conclude that a person is underweight and increases hunger and appetite and reduces metabolism to create the calorie surplus needed to bring body weight back up to its established set point. Once this person gains enough weight, the brain will normalize hunger, appetite, and metabolism to maintain what it thinks is their ideal weight.

What does all of this mean if you are overweight? Even though a person can step on a scale and know instantly that they are overweight, leptin interference fools the brain into thinking that its body weight is at its established ideal.

This malfunctioning body fat feedback system is responsible for the infamous yo-yo diet effect: An overweight person will often use forced calorie restriction to try and get rid of 10-20 extra pounds. Unfortunately, because the brain thinks that this heavier weight is actually its ideal body weight, a forced restriction of calorie intake appears like starvation. The brain will defend itself from this perceived starvation by increasing hunger and appetite and lowering metabolism. Eventually, the dieter will be unable to sustain the forced calorie restriction necessary to maintain their lower weight as the brain succeeds in getting back every pound this person lost. (9)

Different Types of Overweight
While researching for the causes and mechanisms of obesity, I discovered that there are primarily two different types of body fat involved in overweight: Subcutaneous and visceral. A person can suffer from one or both.

Here are two different examples of what "overweight" can mean. The man on the left carries a lot of visceral (abdominal) fat. The man on the right has excess subcutaneous fat.

Subcutaneous fat sits just under the skin and is used for long-term fat storage. Extra consumed calories gets stored in these long-term fat cells.

Since the role of subcutaneous fat is to provide long-term reserve fuel,  if a person has too much subcutaneous fat, then they are overeating (creating a calorie surplus). However, as I have already discussed in another post, the term "overeating" is very complex and can't be adequately explained by the simple idea of "calories in vs calories out."

Visceral fat, on the other hand, is used for short-term, emergency fat storage located in the abdominal cavity. Consequently, there shouldn't be much fat stored in visceral fat cells. 

Interestingly, chronic stress has a unique connection to excessive visceral fat. (10,11,12) When visceral fat is used for long-term storage--giving a person a thicker waist or conspicuously large belly--then they are likely suffering from a chronic elevation of the stress hormone cortisol (a.k.a., chronic stress). (And stress is anything that produces a stress response, not just mental anxiety. Other stressors include a poor dietchronic infections, and too much exercise.)

And when it comes to your body fat and your health, excess visceral fat (which produces the characteristic potbelly or beer belly) indicates major dysfunction in the body more than excess subcutaneous fat. Unlike subcutaneous fat, too much visceral fat is associated with increased risk of heart disease, stroke, and high blood pressure.

Insulin Resistance and Carbohydrate Sensitivity
I should also point out that anyone who is suffering from chronic excess blood levels of cortisol will also be insulin resistant (due to cortisol's counter-regulatory effect on insulin). (10) Anyone who is insulin resistant will also likely be sensitive to excessive carbohydrate intake, with much of these consumed carbohydrates being stored in visceral fat stores.

Eliminating the source(s) of chronic stress (and other causes of insulin resistance like excessive inactivity) can correct this problem, allowing formerly insulin resistant individuals to eat safe carbohydrates like white potatoes and rice can be eaten without fear of weight gain. (13)

If you are overweight, it is likely that you are suffering from chronic stress and/or your brain believes that it is starving. These two causes prevent your brain from accurately controlling your body weight, appetite, and metabolism.

Ultimately, becoming overweight is not the normal consequence of aging, but another indicator of poor health. If someone has too much subcutaneous fat, then they are simply overeating. If someone has too much visceral (abdominal) fat, then they are suffering from a chronic excess of cortisol (i.e., too much stress). Both problems can be corrected with a Paleo-like diet that avoids the 7 Deadly Foods.

Once you get your weight under control, you may find that your body fat percentage is not exactly where you want it to be. Because it is impossible to "burn" this extra fat without building muscle, I will discuss the best ways to improve your body composition in my next post.

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