Health At Every Size: The Surprising Truth About Your Weight (6 page)

 
PART ONE
 
Deconstructing Weight
 
ONE
 
We’re Wired to Maintain a Healthy Weight
 
S
uppose you had a “fat meter” that would send a loud “STOP!” message to your brain once you’d accumulated enough fat. Suddenly, you’d have no desire for pizza, ice cream, or potato chips. You’d look at these favorite foods, even smell their enticing odors, and wouldn’t even be tempted. Or maybe you would decide to eat anyway, and your metabolism would just rev up to burn off the extra calories.
 
Nice fantasy, huh? Well, it’s not so far-fetched. Believe it or not, you do have that built-in mechanism. Why, then, you’re asking, do you always feel driven to eat, even though you consider yourself overweight or struggle to maintain your weight? And why do you gain weight when you aren’t restraining yourself?
 
Well, maybe your meter is broken. Or maybe its alarm isn’t loud enough to trigger a reaction from your brain. And that’s too bad. Because this mechanism is so powerful that people for whom it works never have to fight the temptation to eat when they’re not hungry. Remaining at a healthy weight comes naturally to them; it’s not something they have to work at through deprivation diets and long hours at the gym.
 
Unfortunately, for too many of us this potent weight regulation system has gone awry. Food still tempts us long after our caloric need is satisfied. And extra calories result in packing on extra pounds. Our bodies no longer know how to regulate its “setpoint,” the level that is biologically ideal for us.
 
But don’t worry. By the time you finish this book, you will have learned how to reset this powerful mechanism so that your body can naturally achieve its healthiest weight. You’ll be able to eat normally without thinking about calories, allowing your hunger/fullness/ appetite levels to regulate what and when you eat in a remarkably efficient mechanism. Eating will be simple and enjoyable.
 
Setpoint: Your Ideal Weight
 
When it’s working right, this weight-regulation mechanism is as precise as the most sophisticated scientific instrument. Don’t believe me? Just consider a fifty-year-old woman who weighs about five pounds more than she did when she was twenty. If she eats about 2,000 calories a day, over the course of thirty years she takes in about 22 million calories. Since five pounds of body fat stores about 17,500 calories, that means that her body was just .08 percent off in balancing energy in vs. energy out. This amounts to a difference of about 50 calories per month—less than the calories in one egg!
 
In other words, her energy balance was regulated with a precision greater than 99.9 percent!
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How many things in life can you say that about? Certainly there’s no way you can be as precise by trying to exert your own willpower over what you eat and how much you exercise.
 
Until recent decades, adult weight stability over long periods of time was the norm and was an effortless process. One 1970s research study showed that the average weight of a sixty-year-old man was only four to five pounds more than the average thirty-year-old man.
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That kind of weight maintenance is no accident.
 
So why fight? Give up counting calories and trying to control your eating through dieting. Instead, let your body do the regulating for you. I promise you’ll have far better results.
 
The healthy weight that your body aims for is called your
setpoint weight
. Think of it as the preferred temperature on a fat thermostat. Like any thermostat, this one can be set at whatever point is most comfortable. The system then works tirelessly to do anything it can to bring your body into alignment with that point. It acts like a biological force: The further you go from the center, the stronger the pull to get you back to the comfortable range.
 
This system only works if we let it, however. If you keep “jiggling” with the thermostat via diets, the mechanism breaks down. This jiggling is like a power struggle to wrest control away from your body’s innate weight-regulation mechanism, and in the end, it only makes your body fight harder to retain control. The result: Your body forces you to not only regain any weight you’ve lost, but you may even pay a penalty with extra weight gain—and a setpoint now set higher to protect against future diets.
 
Rather than continuing to engage in this weighty battle with your body, you could declare a truce and join forces with it to help achieve a healthy, natural weight. You’ll find that you will become less interested in eating when you are full. And your body itself will make up for those occasional party overindulgences without you having to deliberately deny yourself.
 
Your Body: A Weight Control Freak
 
Let’s look more closely at just what a control freak your body is when it comes to maintaining the “right” level of body fat.
 
To better understand this concept, we need to take a closer look at your body’s weight-regulating bag of tricks.
 
Picture this: You’re out for an afternoon stroll, enjoying the warmth of the sun on your back. It’s actually a bit too warm, so your body’s automatic cooling system kicks in and you start to sweat, which reduces your core temperature and you feel cooler. Suddenly, dark clouds cover the sun and you feel
too
cool. Again, your body’s automatic thermostat kicks in. The hairs rise on exposed body parts to trap air, goose pimples appear, and you begin shivering, all of which increases your temperature.
 
Do you control any of this? Of course not. Like breathing and digestion, these regulatory actions are governed by your autonomic nervous system, which works in the background without any conscious thought. All these systems are designed to maintain
homeostasis
, or balance, throughout your body.
 
Your body’s attempt to maintain homeostasis is one of the most fundamental concepts in biology. Many physiological variables—such as oxygen levels, carbon dioxide levels, blood volume, and blood sugar—are tightly regulated under this system. For each, your body accepts a certain range with various physiological mechanisms preventing disastrous dips or curves.
 
The amount of body fat you have is similarly tightly regulated. More than fifty years of research proves that your body tries to maintain your fat at the level at which you are designed to function best (not necessarily a size 4 or even 24, however).
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Your body is strongly invested in helping you maintain this healthy and relatively consistent weight, and it has amazingly efficient mechanisms in place to pull off this feat.
 
Unfortunately, recent lifestyle and environmental changes mess with this programming. We further throw the system off when we try to take control through dieting. The result: escalating weight.
 
Understanding Homeostasis
 
The chief ruler of your weight setpoint is your hypothalamus, a small region of the brain that acts as an intermediary between your brain and body.
 
The hypothalamus is a kind of all-knowing sensor. It picks up on sensations like the delicious smell from a just-baked cheese pizza, the burn you got on the roof of your mouth from biting into that pizza too quickly, and that overstuffed feeling from scarfing down too many pieces of said pizza. It’s also tuned in to body states you’re not aware of, like how much body fat you have at any given moment.
 
The hypothalamus reacts to the messages it receives by signaling other body tissues to release hormones, enzymes, and other chemicals to push you back into homeostasis.
 
For instance, if you’re losing weight and you are below your setpoint, your hypothalamus might direct other body systems to regulate your eating and activity levels as well as your metabolic efficiency, the rate at which you burn calories, to get you to regain the weight.
 
At first the hypothalamus enlists your help. It can initiate the release of particular hormones that influence your appetite and mold your drive to eat, including changing how food tastes and how much it appeals to you. It can also lead you to actually crave higher-fat food if it wants you to get concentrated energy and gain weight. It can even decrease your drive to move, leading to serious couch potato behavior.
 
These actions are particularly strong if the hypothalamus senses that body fat levels are dropping too far below the setpoint. Under-eating sets you up for brain activity that produces an urge to eat way beyond the ability of food to satisfy your hunger.
 
Of course, sometimes we’re able to temporarily override the hypothalamus’s efforts to restore homeostasis. For instance, if you’re trying to lose weight, you may be able to consciously overcome feelings of hunger through your own willpower. People on diets manage this—albeit not for long. Or perhaps you don’t want to cancel on your friend, so you make it to the gym despite your feeling of lethargy.
 
So then your hypothalamus gets more aggressive, affecting systems beyond your conscious control. You may feel cold, a sign your body is trying to conserve energy by sending less blood to the periphery, reducing your metabolic rate. Or you might feel sluggish, another sign that your metabolism has slowed. Conversely, you may feel hot after a big meal because your brain has boosted the metabolic effects of food to help your body burn off the extra calories.
 
Need some convincing that your body—not you—is really in control? Consider some of the following studies.
 
Of Rats and Setpoints
 
Some strains of rats have higher weights than others. Observing their growth, scientists determined that genetically heavier strains of rats ate more than thinner rats during adolescence and early adulthood, until they settled into a stable, setpoint weight. Once they reached their setpoint, they ate amounts similar to the thinner rats.
 
Ordinary adult rats, given unlimited access to food and opportunity for exercise, maintain stable setpoint weights. If food is restricted and then provided again, the rat knows just how much to eat to return to its setpoint weight. Fat, thin, or somewhere in between, it didn’t matter: The rat returned to its setpoint weight once food was accessible again.
 
When a Rat Is Hungry
 
To examine the role of the hypothalamus in setpoint control, early researchers used two sources of evidence. Both involved placing an electrode directly into the brain of a laboratory rat. The electrode either damaged that section of the brain so it no longer functioned or stimulated that section of the brain to produce more neural activity.
 
The researchers focused on two sections of the hypothalamus they identified as playing a large role in eating behavior: the lateral hypothalamus (LH) and ventromedial hypothalamus (VMH).
 
When the LH was damaged and dysfunctional, the rats refused to eat and eventually died.
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But when the LH was electrically stimulated and turned on, the rats ate, even if they were full, and got fat.
9
This behavior led scientists to conclude that the LH housed the “hunger center.” Turn it on and we want to eat; turn it off and we’re no longer hungry.
 
In another experiment, the scientists again created lesions in the LH, damaging the appetite center. Although the rats again stopped eating and lost weight, this time the scientists force-fed them to keep them alive.
10
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Eventually, the rats started eating on their own. At some point their weight stabilized, although at a much lower level than before the lesion. In other words, they now had a lowered setpoint.
 
In other experiments, scientists examined how the rats expended energy after losing weight due to the destruction of the LH. They hypothesized that if a rat’s setpoint was reduced, the rat’s body would try to maintain the lowered setpoint and resist weight loss or gain.
 
In fact, that’s just what happened. When the rats with the LH lesions were force-fed to gain weight to their previous levels, their metabolic rate increased substantially so they burned more calories.
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In other words, restoring their old weight caused their body to use mechanisms to get them back to their new setpoint weight. Conversely, reducing their weight from the lower levels they were already maintaining caused a sharp decline in their metabolic rate so they could conserve calories and return to their setpoint. Fat or thin, it didn’t matter: All rats returned to their setpoints.
 
The scientists concluded that the LH must not be the only hunger center, because if it were, the rats wouldn’t have regained their drive to eat. Instead, they suggested, the LH must work in concert with other areas of the brain to regulate hunger and determine setpoint. Further research determined they were right.

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