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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.

Figure 3.5 Stop Sign Food entering the small bowel stimulates release of the substance CCK into the wall of the stomach. That’s where the vagus nerve senses that we’re full and informs the satiety center in our brains to tell our hand to put down the buttered popcorn.

FACTOID

While the majority of taste buds are located on your tongue, you also have taste buds on the roof of your mouth.

Without having to go through the chemical pathways of your body (your bloodstream), CCK acts as a very direct message and indicator of your fullness. (Remember, leptin is more of a long-term indicator of your satiety; CCK provides a very short-term, intense message.)

After the food spends some time in your stomach, it will slowly leave that reservoir and go into the small intestine via the duodenum, the first part of your intestines that comes right after the stomach. That’s when CCK puts up a digestive detour sign, in a very clear physical signal that makes you feel full. It causes the pylorus—the opening at the end of the stomach—to slam shut; that keeps food from moving into the small bowel. That’s how your stomach gets full physically and how you feel full mentally. One interesting note: High-saturated-fat diets lead to less CCK sensitivity, so you do not feel as full as you should after eating a steak.

After the stomach, your food enters the small intestine and has a head-on collision with bile. Bile is the thick green digestive fluid that’s secreted by the liver, stored in the gallbladder, and released into the small intestine. (CCK also has a third effect: It’s what causes the gallbladder to contract.) After fat is broken down into smaller particles by substances called lipases, which are released by the pancreas, these tiny particles interact with bile to form a compound that is easily absorbed by the cells of your body. Bile surrounds the fat in our meal like soap surrounds grease on our hands so it can be scrubbed from the intestinal wall and better digested and absorbed.

Once it reaches the bloodstream, food continues to influence how hungry you may feel. Elevated blood sugar sends your brain the message that it’s time to take your plate to the sink and hit the couch. When your blood sugar is low, that’s what stimulates hunger and causes you to feed like a rat in the Kraft aisle.

Many of us get into trouble when we eat foods with simple sugars (think soft drinks, jelly, cake). Simple sugars create a rebounding effect. You’re feeling blah, so you eat a 3 Musketeers. That sugar surge works like an electrical jolt, and you instantly feel more energy. But less than two hours later, that energy surge (in the form of elevated blood sugar levels) plummets, and then you feel blah again. Your conclusion? You must need another Musketeer. That rebound effect (combined with the desire for the taste that’s stimulated by the pleasure center in your brain) can put your body in biological turmoil, where you eat to feel better, though what you’re eating is actually making you feel sluggish, so you swirl and swirl around, always feeling like you need to eat.

The Word on GERD

Fat doesn’t just pose problems for your belly and subway turnstiles; it also can mess with your throat. About half of obese people have the chest-burning condition called GERD (gastroesophageal reflux disease). The thinking is that extra fat in the belly pushes down on your stomach, thereby opening the angle of the GE junction and pushing it toward the chest. (Remember, it’s at an acute angle to keep food from going back up your throat every time you eat.) The pried-open angle makes it easier for acid and food to be pushed back up. Plus, the extra fat in the belly puts pressure on the contents of your bowel. More pressure, more GERD. What’s the big deal? Besides the unpleasant sensation of tasting your food on the way up, GERD also burns your esophagus-in the same way that the sun burns your skin. After a burn, it takes a couple days to heal, but if the burning happens over and over, it means you’re burning the tissues and are more likely to develop cancer there, just like repeated sunburns increase your risk of skin cancer. Taking half a full aspirin or two baby aspirin (you want 162 mg) with a glass of water decreases this risk by about 35 percent. By the way, alcohol, coffee, pepper, acidic foods like tomatoes and OJ, and, to a lesser degree, chocolate increase GERD symptoms. The best way to manage symptoms until you lose weight is to avoid meals within three hours of bedtime and to put blocks under the head posts of your bed so that you sleep at a slight tilt. (Pillows usually don’t work, since your head will typically roll off the pillow.)

YOU-reka! At the bottom end of your small intestine (before it joins your large intestine), food hits the ileal brake—another signal that you’re full. At this juncture there’s a traffic signal that slows the passage of the slurry of intestinal contents from the small intestine to the large intestine. It’s called the ileocecal valve. The squeezing required to overcome this traffic signal valve is reduced naturally by some foods, since your body feels that you’re still digesting and not ready to evacuate those foods yet. Very little absorption of nutrients occurs in the colon, so once the food passes the ileocecal valve, not much more happens except that you reabsorb water while consolidating the waste you’ve formed. The result: You have a traffic backup in your gut, and if you try to send more cars down the road, the problem’s only going to turn into a fuller feeling. It’s one of the reasons why fiber kills cravings, because fiber slows down the transit of food from your small intestine to your large intestine, keeping that full feeling. In the next chapter, we’ll pick up the rest of the digestive journey in the intestines, where some of the key fat-storing processes take place.

Figure 3.6 Acid Trip Fat presses on the gastroesophageal junction and unkinks this connection, which makes acid and reflux move up toward the throat. Pressure on the stomach from intra-abdominal fat increases the backwash.

The System of Satisfaction

Though it may seem that we have endless reasons to eat-to celebrate holidays, to beat stress, to pass time between Super Bowl commercials-there’s only one real reason why we need food: for energy. That energy allows our organs to function, our muscles to move, and our bodies to keep warm. And to a large extent our brains help control how we convert food to energy. To help understand the process that your body goes through to use energy, we’ll break down the metabolic path into two phases.

 Digestive Phase: Your hypothalamus orchestrates this phase of metabolism by receiving signals from throughout your body about whether you’re hungry or not so that your body can use energy to power itself. Here’s how: Your body has a short-term reservoir for energy in the form of glycogen, a carbohydrate primarily stored in your liver and muscles. After eating, when you have glucose (sugar) and insulin (the hormone produced in the pancreas to transport glucose), your body uses all of the glucose it needs for immediate fuel but takes the rest and stores it as glycogen. If your blood glucose level falls, your pancreas stops releasing insulin-and then releases another G substance, glucagon, which converts the stored energy (glycogen) to sugar (glucose). So the effect is that when your intestinal gas tank empties of sugar (in other words, when our ancestors were fasting between bison hunts), your body is still able to supply crucial energy to your central nervous system by converting glycogen to glucose.

 Fasting Phase: When you’re sleeping or go long periods without eating, your body needs to have a supply of energy to keep your organs functioning. Once you use up all of your available glucose during the digestive phase of metabolism (your body stores only about 300 calories in the short-term glycogen reservoir), it taps a long-term reservoir: fatty tissue in the form of triglycerides (molecules that include a carbohydrate-containing glycerol). This keeps you going until you break the fast with breakfast.

Figure 3.7 First-degree Burning Feasting allows our livers to store excess sugar as glycogen, so we can access energy without eating for hours. Once glycogen stores are full we save the excess energy from an ice cream sundae as fat. To break down fat we first have to use up glycogen, which can take a half hour of exercise. That’s when the body automatically begins burning up fat.

YOU TIPS!

Slow the Process. Especially before your meal. If you have a little of the right kinds of fat just before you eat you can trick your hormonal system by sending the signal to your brain that you’re full. If you eat a little fat twenty minutes before your meal (70 calories or so of fat in the form of six walnuts, twelve almonds, or twenty peanuts), you’ll stimulate production of CCK, which will both communicate with your brain and slow your stomach from emptying to keep you feeling full. (CCK release and ghrelin reduction take about twenty minutes to kick in and take about 65 calories of fat to stimulate.) That way, you’ll be able to sit down for a meal and eat for pleasure, not for hunger-which is one way to ensure you’ll eat less. The average person is finished eating well before his satiety signals kick in, thus counteracting any possibility that his hormones can help him. For the same reason, you should eat slowly. If you down your food faster than a MiniVac, you won’t allow your satiety hormones time to kick in.

Set the Early Fiber Alarm. Many of us may associate fiber with better health and increased toilet time, but fiber is the speed bump of your GI interstate. It slows everything way down. Technically, it works by slowing the transit of food across the ileocecal valve, keeping your stomach fuller for longer. The result: a greater feeling of satiety and an increase of appetite-suppressing CCK-like signals. While you should aim for around 30 grams of fiber a day, the key is bulking up in the morning. Studies show that consuming fiber in the morning (at breakfast) makes you less hungry in late afternoon-a notorious candy-sucking, diet-busting time of day. Great sources of breakfast fiber include oatmeal, cereal, whole grains, and fruit. (You’ll note that every breakfast in the YOU Diet-see Part 4-has a lot of fiber in it, whether it’s the cereal or the vegetables in an egg white omelet or the whole wheat bread. And morning snacks, like an apple, also have fiber.)

Besides controlling blood sugar levels and decreasing insulin levels, fiber also reduces calorie intake for up to eighteen hours a day. Start with 1 to 2 grams of dietary fiber before meals and at bedtime and slowly increase to 5 grams. (If you add it all at once, you’ll produce more gas than a Saudi oil field.) The supplement konjac root also seems to have a fiber-related effect. One study showed a nearly six-pound weight loss in eight weeks for those who ate 1 gram of it an hour before their meals.

Step Down to the Plate. Monstrous portion sizes are one of our stomach’s biggest enemies: Studies show that when you’re served bad foods in large containers, you’ll eat up to one-third more than if you were served in smaller containers. By getting served in larger popcorn boxes, bigger dishes, and taller cups, we’ve automatically been tricked into thinking that availability should dictate how much we eat rather than physical hunger. You don’t have to go through drastic changes to make small ones. For starters, change your serving plates to the nine-inch variety to give yourself the visual and psychological clue that you’re full when your physical appetite has been sated. That’s important because studies show visual clues help determine how full you are, in that you may not feel satisfied until your plate is clean, no matter how large the plate is. That’s also reason never to eat directly out of a box or carton and always to remember that one serving size of a food is often about the size of a fist.

Slow Down. Stomach growling stimulates appetite, but growling doesn’t really tell you how hungry you are. It tells you to eat but not how much to eat. That’s why meal size is so important. You’re hardwired to eat but you’re not hardwired to eat a lot. Having a big meal quickly won’t stop you from wanting to eat a few hours later. So slow down and let your CCK act; it takes about twenty minutes after the nuts to decrease your desire to eat.

Add Pepper. Red pepper, when eaten early in the day, decreases food intake later in the day. Some credit the ingredient capsaicin for being the catalyst for decreasing overall calorie intake and for increasing metabolism. It also appears to work by inhibiting sensory information from the intestines from reaching the brain, which is particularly effective in reducing appetite in low-fat diets. Capsaicin works by killing—or at least stunning-the messages that you’re hungry. So add red peppers to your egg-white omelet.

YOU Test

Are You a Supertaster?

We all know that foods we like may send others seeking gas masks. But your tongue-related genetics may play an even bigger role in waist management. It could mean that you’re either not getting the right foods, or more prone to downing an after-dinner pie before the check arrives.

If you’re classified as a “supertaster,” you tend not to eat fruits and vegetables because they may taste very bitter, thereby putting yourself at a higher risk of certain diseases and colon polyps because you’re not getting the nutrients from fruits and vegetables. You should supplement your diet with a multivitamin to ensure you’re getting the right nutrients, as well as use fruits and veggies to enliven other things-as in salads and desserts and as moisturizers on breads (tomato sauce works great here). And if you’re an “undertaster,” you may be more prone to eating (and overeating) sweets because it takes more of a taste to satiate you. By the way, researchers say about 25 percent of us are supertasters and 25 percent are undertasters, while the rest of us are regular tasters.

Which taster are you?

 The Saccharin Test: Mix one pack of saccharin (Sweet’N Low) into two-thirds of a cup of water; that’s about the size of the tennis ball. Now taste the water. You’ll probably taste a mix of both bitter and sweet, but see which taste is stronger. If sweet is dominant, then it means you’re probably an undertaster, and if bitter is dominant, it means you’re probably a supertaster. If it’s a tie, you are like half the population, so don’t sweat it. To be sure, you may have to do the test more than once to tease out differences.

 The Blue Tongue Test: Wipe a swab of blue food dye on your tongue and see the small circles of pink-colored tissue that polka-dot the newly painted blue canvas. Those are your papillae. Then put a piece of paper-with a 4-millimeter hole, or the size of a hole punch in three-ring paper-over your tongue. Using a magnifying glass, count the little pink dots you see in the hole. If you have fewer then five dots, it means you’re an undertaster, while more than thirty indicate you’re probably a supertaster.