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In a perfect system, your offense and defense complement each other; you get the foods you need and stop when you’ve had enough. Unfortunately for everyone except elastic-waistband manufacturers, a lot of things can mess up those systems (many of which we’ll discuss in a moment). But these obstacles aren’t insurmountable. You can take comfort (and find motivation) in the fact that your body wants you to reach your goals. Your body doesn’t want to be bigger than it should be. Your body doesn’t want lots of excess fat. Take the case of rats made obese by force-feeding. When they’re allowed to eat freely, they go back to their control weight. They eat what they should eat, without thinking. Same goes for starving rats. When allowed to eat again, they don’t gorge. They naturally go back to their control weight. And we know from years and years of research that what rats do is a pretty fair indication of what humans will do under the same circumstances. (Humans, of course, will do what rats do when they’re motivated only by biology. A rat isn’t upset by stress at home or work, which is why controlling the emotional aspect of eating plays such a big role in effective waist management, as we’ll discuss in Part 3.)

YOU-reka! If you can allow your body and brain to subconsciously do the work of controlling your eating, you’ll naturally gravitate toward your ideal playing weight. You do it by developing a well-trained defense that naturally balances the offense. When you do, you’ll win the diet game every time, whether you have willpower or not. Though it may not always be the case in football or Scrabble, when you pit offense against defense in your body, the offense in your body typically attacks more aggressively. It’s simply easier to scoop up bean dip than it is to leave it for others.

The Hunger On and Off Switches

Duct tape over your mouth isn’t how your body regulates food intake. Your body does it naturally through the communication of substances controlled by your brain. Although there are many hunger- and obesity-related hormones waiting to be discovered, there’s enough evidence to suggest that two hormones have as much influence for dictating our hunger and satiety levels as a head coach does on offense and defense—hour to hour and year to year.

Lovin’ Leptin: The Hormone of Satisfaction

In sumo champions, a little extra fat can produce good results. But we also think that fat has an unfair knock against it. Fat is treated a little like an accused suspect; it sometimes gets a bum rap. Fat produces a chemical signal in your blood that tells you to stop eating. Left to its own devices, fat is self-regulating; the problem occurs when we override our internal monitoring system and continue to stuff ourselves long after we’re no longer hungry. Your body knows when it’s had enough, and it prevents you from wanting any more food on top of that. How does fat curb appetite? Through one of the most important chemicals in the weight-reduction process: leptin, a protein secreted by stored fat. In fact, if leptin is working the way it should, it gives you a double whammy in the fight against fat. The stimulation of leptin (the word comes from the Greek word for “thin”) shuts off your hunger and stimulates you to burn more calories—by stimulating CART.

FACTOID

Neuropeptide Y is a stress hormone that increases with severe or prolonged stress. This may be why some people in chronically stressful situations tend to gain weight. Testosterone, the male sex hormone, seems to stimulate NPY secretion, while the female sex hormone, estrogen, seems to have a varying effect depending on the stage of a woman’s cycle.

But our bodies aren’t always perfect, and leptin doesn’t always work the way it’s supposed to. In some research, when leptin was given to mice, their appetites decreased, as expected. When it was given to people, they initially got thin, but then something strange happened: They overcame the surge of leptin and stopped losing weight. This indicates that our bodies have the ability to override leptin’s message that our tank is full. How? When leptin tells your defense—the satiety chemicals—to kick in and protect you against stray bonbons, the pleasure center in your brain says, “Uh, yeah, three more this-a-way” That surge from the pleasure center, which we’ll discuss in more detail in part 3, can overrule leptin’s messages that you’re full. That’s called leptin resistance (there’s another form of leptin resistance as well, which happens when cells stop accepting leptin’s messages). Most obese people, by the way, have high leptin levels; it’s just that their bodies have the second form of leptin resistance—they don’t receive and respond to leptin signals.

That doesn’t mean leptin is always on the losing end of this chemical battle. YOU-reka! The challenge is to let leptin do its job so that the brain demands less food. One way to do it: Walk thirty minutes a day and build a little muscle (that’s part of our activity plan in part 4). When you lose some weight, your cells become more sensitive and responsive to leptin.

FACTOID

Scientists found how ghrelin works accidentally: in gastric bypass surgery, doctors cut out the part of the stomach that secretes ghrelin. They soon realized that it wasn’t just the smaller stomach but the reduced ghrelin production that helped surgery patients eat less food. The eat-everything signal was shut off, clearing the way for the satiety center to take care of its business.

Ghrelin Is the Gremlin: The Hormone of Hunger

Your stomach and intestines do more than hold food and produce Richter-worthy belches. When your stomach’s empty, they release a feisty little chemical called ghrelin. When your stomach’s growling, it’s this gremlin of a hormone that’s controlling your body’s offense; it sends desperate messages that you need more points, you need to score, you need to FedEx the chili dogs to the GI tract immediately. Ghrelin makes you want to eat—by stimulating NPY. YOU-reka! To make things worse, when you diet through deprivation, the increased ghrelin secretion sends even more signals to eat, overriding your willpower and causing chemical reactions that give you little choice but to line your tongue with bits of beef jerky.

Ghrelin also promotes eating by increasing the secretion of growth hormone (ghre is the Indo-European root word for “growth”). So when you increase ghrelin levels, you stimulate that growth hormone to kick in, and growth hormone builds you not only up but out as well.

Your stomach secretes ghrelin in pulses every half hour, sending subtle chemical impulses to your brain—almost like subliminal biological messages (carrot cake, carrot cake, carrot cake). When you’re really hungry or dieting, those messages come fast—every twenty minutes or so—and they’re also amplified. So you get more signals and stronger signals that your body wants food. After long periods, your body can’t ignore those messages. That’s why sugar cookies usually trump willpower, and that’s why deprivation dieting can never work: YOU-reka! It’s impossible to fight the biology of your body. The chemical vicious cycle stops when you eat; when your stomach fills is when you reduce your ghrelin levels, thus reducing your appetite. So if you think your job is to resist biology, you’re going to lose that battle time after time. But if you can re-program your body so that you keep those ghrelin gremlins from making too much noise, then you’ve got a chance to keep your tank feeling like it’s always topped off.

Food Fight: The Ghrelin Versus Leptin Grudge Match

So now let’s get back to that offense and defense. The natural state is for you to have a give-and-take relationship between your eating and satiety chemicals—between your ghrelin and leptin levels—to influence NPY and CART, respectively. It’s the relationship between the impulse that says, “I’ll take a large pepperoni with extra cheese,” and the one that says, “No more passengers, this belly is full.”

This battle over eating isn’t between your willpower and the Belgian waffles; it’s between your brain chemicals. The NPY is the villain—encouraging you to buffets, driving you to the pantry, pointing its chemical finger to the convenience foods, while CART is your dietary guardian angel, which encourages a cascade of allies to keep you full and satisfied and in no way interested in creamed anything. Think of the two substances—NPY and CART—competing for the same parking space, the one that will ultimately determine whether or not you eat (see Figure 2.3). They both arrive at the same time and want that space. Either more NPY or more CART sneaks into the spot, thus sending the all-important go or stop signal to your brain to influence the hormones that make you feel full or hungry.

Here’s how they all work together: Ghrelin works in the short term, sending out those hunger signals twice an hour. Leptin, on the other hand, works in the long term, so if you can get your leptin levels high, you’ll have a greater ability to keep your hunger and appetite in check. Isn’t that great? Leptin can outrank ghrelin—to keep you from feeling like feasting on anything short of fingernails every few minutes. If you focus on ways to influence your leptin levels, and, more important, leptin effects (through leptin sensitivity), your brain (through CART) will help control your hunger.

Sometimes, it may seem like we don’t have much control over the chemical reactions taking place within our arteries or inside our brains. But just as you can control things like cholesterol and blood pressure by changing the foods you eat or altering your behaviors, you can also control the satiety center of your brain. How? Through your choice of foods.

Figure 2.3 In a Jam The satiety center is waiting to be turned off by NPY or stimulated by CART. Whichever fills up the receptor docks first is what controls whether you want to eat more or not. In turn, these two proteins are influenced by lack of water, sleep, and even sex. They’re also influenced by ghrelin coming from your stomach, which stimulates NPY so you get hungry, and leptin from your fat, which is further stimulated by a chemical called CCK, released from your intestines after a meal.

At least as far as your body is concerned, foods are drugs; they’re foreign substances that come in and switch around all those natural chemical processes going about their business within your body. When your body receives foods, different chemical reactions take place, and messages get sent throughout your system—turning on some things, turning off others. While your body internally gives orders, you set the tone and direction of those orders through the food you’re feeding it. Eat the right foods (like nuts), and your hormones will keep you feeling satisfied. But eat the wrong foods (like simple sugars), and you’ll cause your body to go haywire hormonally, and that ends up with one result: the next notch in your belt.

A major gang leader against your body is fructose, found in high-fructose corn syrup (HFCS), a sweetener in many processed foods. Here’s how it works: YOU-reka! When you eat calories from healthy sources, they turn off your desire to eat by inhibiting production of NPY or by producing more CART. But fructose in the HFCS, which sweetens our soft drinks and salad dressings, isn’t seen by your brain as a regular food.

Because your brain doesn’t see any of the fructose in the thousands of HFCS-containing foods as excess calories or as NPY suppressants, your body wants you to keep eating (which means that even low-fat foods can have extremely bad consequences, calorie- and appetite-wise). Americans have gone from eating no pounds of this stuff per person in 1960 to eating more than sixty-three pounds of it every year (that’s 128,000 calories). That’s a contributor to weight gain, since the fructose in HFCS doesn’t turn off your hunger signals. Foods with fructose—which may in fact be labeled as low-fat—make you both hungry and unable to shut off your appetite. They are also rich sources of calories: the perfect storm of weight gain. So you constantly get the signal that you’re hungry, even after you’ve jammed your gut with two baskets of calorie-laden, fructose-loaded biscuits.

YOU TIPS!

Get Over Sticker Shock. You should read food labels as actively as you read the stock ticker or the horoscopes. Don’t eat foods that have any of the following listed as one of the first five ingredients:

 Simple sugars

 Enriched, bleached, or refined flour (this means it’s stripped of its nutrients)

 HFCS (high-fructose corn syrup-a four-letter word).

Putting them into your body is like dunking your cell phone in a glass of water. It’ll cause your system to short out your hormones and send your body confusing messages about eating. Today’s yearly per capita consumption of sugar is 150 pounds, compared to 7.5 pounds consumed on average in the year 1700. That’s twenty times as much! When typical slightly overweight people eat sugar, they on average store 5 percent as ready energy to use later, metabolize 60 percent, and store a whopping 35 percent as fat that can be converted to energy later. Any guess as to where 50 percent of the sugar we consume comes from? HFCS in fat-free foods like salad dressings and regular soft drinks.

Choose Unsaturated over Saturated. Meals high in saturated fat (that’s one of the aging fats) produce lower levels of leptin than low-fat meals with the exact same calories. That indicates you can increase your satiety and decrease hunger levels by avoiding saturated fats found in such sources as high-fat meats (like sausage), baked goods, and whole-milk dairy products.

Don’t Confuse Thirst with Hunger. The reason some people eat is because their satiety centers are begging for attention. But sometimes, those appetite centers want things to quench thirst, not to fill the stomach. Thirst could be caused by hormones in the gut, or it could be a chemical response to eating; eating food increases the thickness of your blood, and your body senses the need to dilute it. A great way to counteract your hormonal reaction to food is to make sure that your response to thirst activation doesn’t contain unnecessary, empty calories-like the ones in soft drinks or alcohol. Your thirst center doesn’t care whether it’s getting zero-calorie water or a mega-calorie frap. YOU-reka! When you feel hungry, drink a glass or two of water first, to see if that’s really what your body wants.

Avoid the Alcohol Binge. For weight loss, avoid drinking excessive alcohol-not solely because of its own calories, but also because of the calories it inspires you to consume later. Alcohol lowers your inhibition, so you end up feeling like you can eat anything and everything you see. Limiting yourself to one alcoholic drink a day has a protective effect on your arteries but could still cost you pounds, since it inhibits leptin.

Watch Your Carbs. Eating a super-high-carb diet increases NPY, which makes you hungry, so you should ensure that less than 50 percent of your diet comes from carbohydrates. Make sure that most of your carbs are complex, such as whole grains and vegetables.

Stay-Va-Va-Va-Voom-Satisfied. In any waist management plan, you can stay satisfied. Not in the form of a dripping double cheeseburger but in the form of safe, healthy, monogamous sex. Sex and hunger are regulated through the brain chemical NPY. Some have observed that having healthy sex could help you control your food intake; by satisfying one appetite center, you seem to satisfy the other.

Manage Your Hormonal Surges. There will be times when you can’t always control your hormone levels; when ghrelin outslugs your leptin, and you feel hungrier than a lion on a bug-only diet. Develop a list of emergency foods to satisfy you when cravings get the best of you-things like V8 juice, a handful of nuts, pieces of fruit, cut-up vegetables, or even a little guacamole.

Chapter 3
Eater’s Digest
How Food Travels through Your Body

Diet Myths

 Fat turns to fat, protein turns to muscle, and carbs turn to energy.

 The fullness of your stomach is what tells you to stop eating.

 Sugar gives you an instant high to help combat hunger.

Once your brain tells you to eat, that’s exactly what you do. You eat. Maybe you gorge. Maybe you nibble. And then maybe you forget about that hefty portion of mac ’n’ cheese until it winds up on the back of your thighs. But in between mouth and thighs, there’s an amazing system of digestion that takes place—a system that determines whether that food gets burned, stored, or expelled faster than a delinquent high schooler.

Now that you know the biochemical reasons why you shuttle food to your mouth, it’s time to start exploring the biology of what happens to food once it’s in there. In this chapter, we’ll discuss what happens in the early part of your digestive system, and in the next chapter, we’ll discuss the effects of food as it interacts with the rest of your digestive organs.

Your Digestive Highway: The On-ramp

On your gastrointestinal interstate, everything enters via your physiological toll booth: your mouth. The nutritious powerhouses slide through the express toll to give you the power, energy, stamina, and strength to live your life. Toxic (though sometimes tasty) foods can enter too, but you’ll pay a heavier toll later for the damage they do along the way and after. Throughout its journey, your food and all of its nutrients (and toxins) will pull over at various organs, slow down on winding roads, speed up, merge with other nutrients, and even get pulled over by the bowel brigade for nutritional violations. (See Figure 3.1.)

During every trip, your food hits a symbolic three-pronged fork in the road:

 Either it will be broken down and picked up by your bloodstream and liver to be used as energy.

 Or it will be broken down and stored as fat.

 Or it will be processed as waste and directed to nature’s recycling pot: the porcelain junkyard.

Figure 3.1 Gutting It Out Food pulls over at various spots in the intestinal track so disease of these areas can cause nutritional deficiencies even if two people are eating the identical foods. Not all of the nutrients that come from food and supplements get absorbed in the same place; they’re absorbed throughout your GI tract. Here are the rest stations where nutrients are absorbed:

 Stomach: alcohol

 Duodenum (first part of the small intestine; takes off from the stomach): calcium, magnesium, iron, fat-soluble vitamins A and D, glucose

 Jejunum (middle part of the small intestine): fat sucrose, lactose, glucose, proteins, amino acids, fat-soluble vitamins A and D, water-soluble vitamins like folic acid

 Ileum (last part of the small intestine; leads to large bowel): proteins, amino acids, water-soluble vitamins like folic acid, vitamin B12

 Colon (also known as the large bowel): water, potassium, sodium chloride

FACTOID

The average person has 10,000 taste buds, which are onion-shaped structures. People regenerate new taste buds every three to ten days, but these regenerate at a slower rate as people get older. Elderly people may have only 5,000 taste buds.

Here’s how the system starts: Before a morsel even reaches the tollbooth, your body has a radar gun to let you know that food is coming—powered by such physiological cues as sight, smell, and the fact that you’ve been drooling like an overheated Saint Bernard at the thought of a fried-cheese appetizer special. In response to that sensory information, glands in your mouth start to secrete enzymes to help break down your food; then your stomach quickly constructs its version of a roadside welcome center by pumping out stomach acid to help prepare your body for the digestion process.

Now, don’t underestimate your stamp licker as a player in this digestion process. Back in the day of buffalo-hide cocktail dresses, people relied on their tongues (and their noses) for survival; if it tasted good, then it was safe, and if it tasted like dinosaur dung, then it could be poisonous or toxic.

FACTOID

Maybe the old days were right: It used to be that young docs would criticize older docs for giving B12 shots, calling them nothing more than placebos. But nearly 40 percent of Americans may suffer from a vitamin B12 deficiency.

We do the same things, but in slightly different ways. Since our bodies use our senses to process information, we rely on our tongue for information about food. The information we acquire sends messages to the brain, and then the brain sends messages to our forks: keep eating or stop eating. That message largely comes from our five tastes (sweet, sour, salty, bitter, and unami, which recognizes the inherent deliciousness in foods like juicy filet mignon), but it also comes from what we smell. Some researchers say that three-quarters of how we “taste” certain foods actually comes from how we smell it. What’s this have to do with your waist growing? For one, there’s the obvious: the more you like a bad-for-you food, the more likely you are to keep eating it. But the genetics of taste and taste buds may play an even more subtle and fascinating role. As you’ll see in the box on page 70 (“Are You a Supertaster?”), the physiological makeup of your tongue could make you more or less disposed to eating good or bad foods.

Figure 3.2 Taste Tester The most powerful muscle in the body, the tongue, tastes food with papillae that sense the chemicals in foods and tell you whether they’re worth your continued attention.

Figure 3.3 Chewing the Fat One of the reasons we can gain weight so readily is the efficiency of our teeth, which fit perfectly with one another to ensure that every morsel of food is crushed completely. Salivary glands near the lower teeth and at the back of mouth secrete enzymes to hasten digestion before swallowing. The sight and smell of food warn these systems of what’s to come.

FACTOID

Eating nuts does not create the calorie intake that you might expect because 5 percent to 15 percent of the calories are not absorbed by the intestinal system. That’s because the nuts’ skin and how well we chew nuts influence digestion. An added bonus: The slow release of calories throughout the intestinal system leads to prolonged satiety.

Unlike other animals, we waste very little energy eating because of our highly efficient perfectly opposing molars (see Figure 3.3). The powerful crushing motion helps us extract every possible calorie from the prime rib deluxe. Other animals waste or burn a lot of calories while they eat because their teeth do not efficiently mush the food when they move prey to belly. In humans, once that food actually does breeze past the toll booth, it accelerates onto the on-ramp of the esophagus—that’s the tube that links your mouth to the interstate that is your GI system.

After your Double Whopper slides down the on-ramp, it has to make a tricky merge in the form of a sharp turn to enter the stomach. That angle—the gastroesophageal junction—is what keeps stomach acid from spilling back into your esophagus and making your chest feel like an arson victim. (When you have extra fat in your belly, that angle is pried open, allowing acid to spill upward and cause heartburn. See “The Word on Gerd,” page 64.) Once your Whopper chunks have entered your stomach, serious digestion begins. The food is held in your stomach until your body directs it to the small intestine, where most of the nutrients are absorbed and passed along to the rest of your body through your bloodstream (to the liver, which is the next stop for absorbed nutrients), or to the large intestine on the way to evacuation.

Food Processor:

How Your Body Breaks Down Nutrients

In terms of weight gain, a calorie is a calorie is a calorie. Calories not used immediately by your body for energy are either eliminated as waste or stored as fat. YOU-reka! But that doesn’t mean that all calories are treated equally by your body. For example, protein and fiber with high water content have a great effect on satiety, and simple carbohydrates have the least effect on satiety. (Fat, by the way, has an effect on satiety similar to that of protein and fiber, which is why low-fat diets leave people hungry all the time.) When it comes to converting calories, your body processes fat most efficiently—meaning that you actually keep more of it, because your body doesn’t need to expend as many calories trying to store it. On the flip side, your body works hard to process protein, to make it highly flammable to your body’s metabolic furnace.

Oh, the Gall

Your gallbladder may seem as unnecessary as bad goatees, but one of its functions is to help store bile-that digestive juice that helps your body absorb nutrients. Obese people have a greater than 50 percent chance of developing gallstones. Why? An overworked liver caused by being overweight makes bile, which is more like sludge than liquid, and predisposes them to developing stones. It’s also more likely that you’ll develop stones when you lose weight fast, like after weight-loss surgery-because the gallbladder doesn’t empty enough when it doesn’t see any fat. So it’s not uncommon for a surgeon to remove the gallbladder during a gastric bypass procedure. The risk factors for developing the painful stones are easy to remember, because they sound like an R & B group. They’re the 4 Fs: female, fertile, fat and forty. (We don’t mean this to be a gender issue, but the fact is that women are more likely to have gallstone symptoms than men.)

Contrary to popular belief, not all ingested protein becomes muscle, and not all the fat in your food gets stored on your hips. Everything has the potential to turn into fat if it’s not used by your body for energy at the exact time it is absorbed through your intestines. And energy is energy is energy (see Figures 3.4a and 3.4b). Here’s how the different nutrients are processed:

Simple sugars (as in a cola): When sugar, which is quickly absorbed and sent to the liver, meets the liver in the digestion process, the liver tells your body to turn that sugar into a fat if it can’t be used immediately for energy.

Complex carbohydrates (as in whole-grain foods). They take longer to digest, so there’s a slower release of the carbohydrates that have been converted in your bowel to sugar to become sugar in your bloodstream. That means your digestive system is not stressed as much. Still, if your body can’t use this slower sugar when it’s released, it gets converted to fat.

Figure 3.4a Department of Energy The three major types of energy are contained in carbohydrates, proteins, and fats, which can come from healthy or waist-busting forms. Complex carbs enter the blood slowly, so we do not tax our hormones. Amino acids are converted inefficiently to sugars, and fats cannot be converted at all. Fats come in forms our bodies recognize (like nuts) and naturally less common forms that poison us (like trans fats). Most foods, like meat, are a combination of energy sources; as the food digests (or sometimes rots) in your intestines, nutrients are absorbed in different places. By the way, even though the liver is the symbolic center of the metabolic universe, the intestines, as evidenced by your bathroom time, aren’t really a closed loop.

Figure 3.4b Food Use Simple sugars from carbohydrates are the most versatile energy source, so they’re preferentially used by our organs, especially the finicky brain, which refuses to tolerate any other source. Fats are a backup system to supply muscle with energy; this is why actually using muscles is needed to selectively lose fat and why exercise works so well. Amino acids from proteins are crucial for building the body, but are used only as a last resource for exercise energy.

Protein (as in meat): It gets broken down into small amino acids, which then go to the liver. If the liver can’t send them to your muscles (say, if you’re not exercising and don’t need them for muscle growth or maintenance), then, yep, they get converted to glucose, which then gets converted to fat if you can’t use it for energy.

Fat(as in funnel cake): It gets broken into smaller particles of fat and gets absorbed as fat. Good fats (like those found in nuts and fish) decrease your body’s inflammatory response, and bad fats increase it. That inflammatory response, which we’ll explain in the next chapter, is a contributing factor to obesity and its complications. If you’re exercising and have used up all readily available carbohydrates (sugar), your muscles can use fat for energy, which is a great way to erode your love handles.

Your Digestive Highway: The Main Drag

At the bottom of your stomach and top of your intestines, your food hits an important traffic signal: It’s the red light that tells your brain you’re full and don’t need another large order of onion rings (or the cheese sauce for dipping or the beer to wash it down). That red light is delivered by the vagus nerve, which is a large nerve that comes from the brain and stimulates the contraction of the stomach (see Figure 3.5). The vagus nerve is also the main cable controlling the parasympathetic system, which is the relaxation section of your nervous system. YOU-reka! The key messenger switching the vagus on is a peptide produced in your gastrointestinal track called CCK, which is released when your bowel senses fat. Technically, it stands for cholecystokinin, but for our purposes, let’s think of it as the Crucial Craving Killer because its main purpose is to tell your brain via the vagus nerve that your stomach feels fuller than a Baywatch bathing suit.