Make food a very incidental part of your life by filling your life so full of meaningful things that you’ll hardly have time to think about food.
—PEACE PILGRIM
I have to admit that I went through numerous versions of this chapter. It started out as a 60-page dissertation on the entire process of digestion, nutrition, metabolism, and the intricate hormonal interactions that affect appetite, fat burning and blood sugar. When I realized that I was starting to talk medicalese—after all, do I need to use the term gluconeogenesis ten times in one chapter?—I knew it was time to go back to square one and answer the really important question: What are the key things about food, energy, metabolism, and endocrinology that you need to know to help you lose weight? So if you want a comprehensive understanding of the whole physiology, I’d suggest a textbook on nutrition or endocrinology, where you can learn the details about gluconeogenesis (including how to pronounce it!). In the meantime, here are the key points that you need to know.
HOW FOOD BECOMES ENERGY
To understand how to lose weight, you first have to understand how food becomes energy in your body. Food is converted into energy by the processes of digestion and metabolism. Let’s use lunch as an example: a turkey sandwich on white bread with mayo, sweetened soda, and spinach salad. Where you see typical components—bread, turkey, mayonnaise, soda, spinach—your body sees carbohydrates (bread, spinach, and soda), protein (turkey), and fat (mayonnaise). Each type of food is digested and metabolized into energy in different ways.
Digestion starts in the mouth, where the act of chewing, along with your saliva, which contains enzymes that start to break down food, work together to moisten and start dissolving food. The food heads down the esophagus into your stomach, where enzymes and acids are released from the stomach lining. The food is chemically broken down, with each type of food headed for a different objective.
Not all foods are digested at the same rate. Carbohydrates (which are not just starches but actually include everything from bread, rice, and sugar, to potatoes, green vegetables, and fruits) are usually digested more quickly than proteins and fats. But how quickly you digest carbohydrates also depends on the type of carbohydrate. For example:
After digestion in the stomach, food moves quickly through your small intestines, where all absorption of nutrients occurs.
Meanwhile, there is another process going on in your bloodstream! Glucose, amino acids, and triglycerides start surging through the bloodstream to be used as energy, help in cellular repair, or stored as fat.
When faced with high amounts of glucose, your pancreas secretes a hormone known as insulin. Insulin’s role is to keep blood glucose levels from rising too high. When insulin is present, glucose—your body’s favorite and most easy-to-use energy source—is taken up by cells, especially the important area known as the mitochondria, sometimes called the powerhouse of the cell, since this is where the largest production of energy occurs.
What happens to the amino acids and triglycerides? Usually, triglyceride fats end up stored in fat tissue. They can be converted into glucose by your liver, but usually only as a last resort when glucose is not readily available, because it costs the body more energy to metabolize these stored fats into energy. In case of a brief starvation, the liver holds a 12-hour supply of glycogen, which it can convert into glucose to help fuel the body. Otherwise, the body is very stubborn about letting go of its fat and amino acid reserves. This is why it can be hard to lose weight, since the body will readily and quite efficiently use all the glucose it gets directly from food.
Once you have finished digesting all the carbohydrates you last ate, your liver will convert its stored glycogen back into glucose and release the glucose to help maintain blood sugar. When the liver runs out of glycogen and in the absence of new carbohydrates or glucose sources, the liver shifts to a process called gluconeogenesis (there’s that word!) and starts converting amino acids into glucose.
As you can see, your metabolism is going to do everything it can to
INSULIN
When you have eaten a concentration of simple carbohydrates—a candy bar and/or a soda, for example—the body generates a strong insulin response to prevent excess blood sugar. This large insulin response in turn can trigger a dramatic drop in blood sugar—sometimes to levels that are even too low—in the 3 to 5 hours after the simple carbohydrate was eaten. When blood glucose levels fall, an adrenaline surge can be triggered, which can then cause nervousness, anxiety, irritability, and even palpitations. (This is the phenomenon observed in some children when they’ve had too much sugar.)
The same up and down pattern of insulin, glucose, and adrenaline levels either doesn’t happen at all or is severely blunted after eating a balanced meal that includes fats, proteins, and fiber in addition to complex carbohydrates, because the processes of digestion and absorption are slowed down.
Higher blood glucose levels can occur for the following reasons:
Insulin resistance can occur in which the brain and some of the body’s cells fail to react to the presence of insulin in the bloodstream.
This condition is not as severe as diabetes, where the cells cannot secrete enough insulin to maintain safe blood sugar levels. Instead, insulin levels may actually be high, yet the pancreas continues to pump out even more insulin in an attempt to store the glucose left in the blood. But the cells cannot react to the insulin that is released, and the glucose continues to circulate in the bloodstream. When you eat, glucose levels rise even higher. After a few years, the overworked pancreas begins to tire and may lose its ability to produce any insulin at all, leading to type 2 diabetes. Insulin resistance is, in fact, sometimes called prediabetes.
The high levels of insulin circulating through the bloodstream also stimulate the storage of fat and amino acids and prevent the breakdown of fat and protein. They also prevent the release of glucagons.
The fat cells in your abdomen are particularly sensitive to high insulin levels and are very effective at storing energy—far more so than fat cells you’d find in other areas such as the lower body (i.e., hips, rear end, thighs). Because abdominal fat cells are so close to your digestive organs and there is an extensive network of blood vessels circulating in the abdominal area, it’s even easier for fat cells to store excess glucose there.
Before it has progressed to full-scale type 2 diabetes, insulin resistance is a reversible condition. Exercise, a reduction in simple carbohydrates, and a reduction in calories can all help to reduce insulin levels. Exercise helps cells respond more effectively to insulin, which then helps reduce the excess glucose in the bloodstream before it is stored as fat. Fewer simple carbohydrates reduce the overall circulating blood glucose levels. And avoiding overeating prevents excess calories from all sources from being released into the bloodstream as glucose. The less glucose, the less insulin; when insulin levels are low, the body turns to fat reserves for energy and starts to break down large fat molecules into fatty acids for easy energy production.
Metabolic Syndrome
Taking insulin resistance a step further results in metabolic syndrome (formerly known as syndrome X). Metabolic syndrome is usually characterized by insulin resistance, plus elevated levels of cholesterol and triglycerides, as well as obesity.
The official diagnostic criteria for metabolic syndrome include
Some experts estimate that as many as 1 in 4—or 47 million—adults in the United States have metabolic syndrome. These numbers are expected to rise as the population ages.
OTHER PLAYERS IN THE PROCESS
Glucagon
As I mentioned, in the presence of glucose your pancreas releases insulin. But if your blood sugar is low—for example, if you haven’t eaten in 4 or 5 hours—the pancreas will secrete glucagon. It’s like the opposite of insulin. Glucagon pulls sugars out of storage, first from the liver, then by converting fatty tissue back into glucose.
The higher the carbohydrate content of your last meal, the more insulin is produced, and the less glucagon your body secretes. This pushes your body toward storing fat. Besides lower blood glucose levels, two other conditions are known to trigger the release of glucagon:
Leptin
Entering into the whole metabolism equation is the issue of leptin, a hormone produced by your fat cells that controls your body’s fat storage responses. When leptin is released by your fat cells, it is communicating to your brain how much fat you have stored. Enough leptin being released to the brain tells the brain—specifically your hypothalamus gland—there is enough fat stored now to avoid starvation, so you can stop eating. The stop eating message is translated into a reduction in appetite and a speeding up in metabolism/energy expenditure.
When the body faces real starvation or perceived starvation such as a dramatic calorie reduction, leptin release is slowed or stopped. Lowered leptin levels communicate to the brain that there is insufficient fat stored to prevent possible starvation, and food intake should be increased. Appetite will rise. This is the mechanism that makes you feel hungry when you go on a particularly low-calorie diet.
Logic would dictate that giving obese people leptin might help with weight loss, but in a rush to create leptin-based drugs this theory was tested and shown to be faulty. Interestingly, obese people tend to have very high levels of leptin. The real problem appears to be that in people who are overweight, it’s not a shortage of leptin that causes difficulties; it’s that the brain is not getting the message. In essence, the brain is leptin resistant, meaning that the brain and metabolism think the body is starving even while the person is eating too much food.
If the brain isn’t getting the right message about leptin in the first place, the metabolic circuit becomes broken. The brain cannot tell the body that enough fat is stored, food intake can slow down, and energy expenditure can rise. More fat will accumulate, and metabolism will slow down further.
Ghrelin
Ghrelin, sometimes referred to as the hunger hormone, is a hormone produced by your stomach that says it’s time to eat now! Ghrelin rises sharply before you eat and falls quickly afterward. The ghrelin signal itself has a short-term effect, lasting up to an hour. If you don’t eat when the signal presents itself, it will go away fairly quickly, and appetite will disappear.
When you lose weight, however, baseline ghrelin levels can go up. One study found ghrelin levels rose an average of 24% in dieters. In this way, it’s thought that ghrelin may be part of the body’s efforts to avoid starvation and maintain a particular weight range.
Adrenal Hormones: Cortisol and Adrenaline
Your hypothalamus, via the pituitary gland, directs the adrenal glands to secrete the hormones cortisol and adrenaline. Cortisol is released as part of your daily hormonal cycle, but both hormones can also be released in reaction to perceived stress—both physical and emotional—as part of the body’s fight-or-flight response that is essential for survival. Adrenaline makes you energetic and alert and increases metabolism. It also helps fat cells to release energy. Cortisol helps your body become even more effective at producing glucose from proteins and is designed to help quickly increase the body’s energy in times of stress.
The problem is that many of us are under a constant state of stress for various reasons. This leads to a constant state of excess cortisol production. Excess cortisol stimulates glucose production. This excess glucose then typically is converted into fat, ending up as stored fat. There are many research studies showing that high levels of circulating cortisol increase the risk of obesity and increased fat storage—particularly abdominal obesity, which is one of the most dangerous types of obesity.
And excess adrenaline production means that the fat cells can become resistant to the effects of adrenaline. Eventually, the fat cells become unresponsive to adrenal stimulation to release fat, but through the presence of high cortisol they’re more responsive to fat storage.
INFLAMMATION
The role of inflammation in metabolism and weight issues is just beginning to be studied. Usually, inflammation is a sign that your immune system is fighting off some sort of infection or attempting to heal an injury. So, for example, when your nasal passages swell during a respiratory infection, your immune system is sending white blood cells and other substances to help fight off germs, viruses, and bacteria to reduce infection.
Some kinds of inflammation, however, are signs that the body is in a state of imbalance. For example, when you regularly eat foods to which you are allergic or sensitive, you can inflame the muscosal lining of your intestines. Eventually, the lining can become less and less able to prevent passage of larger molecules, and large molecules can pass into your bloodstream, a condition known as leaky gut syndrome. This condition has a connection to the development of various forms of autoimmune disease, including thyroid disease, as well as other conditions.
Researchers are now looking at the role of chronic inflammation in weight gain. One study in the Journal of the American Medical Association found that a particular inflammatory marker known as C-reactive protein (CRP) was increased by more than 50% in obese women whose fat concentration centered mainly on their hips and thighs (i.e., pear-shaped distribution) and was increased by more than 400% in obese women whose fat was centered on the waist and abdomen (i.e., apple-shaped distribution).
Interestingly, there are some studies that show exercise can actually reduce levels of inflammatory proteins. Antioxidants in fruits and vegetables also appear to help reduce proinflammatory hormones. And sufficient levels of omega-3 fats (found primarily in fatty fish and flaxseeds) and proper balance with omega-6 fats (found in common vegetable oils like corn, safflower, and sunflower oil) appear to reduce inflammation as well.
METABOLISM
Now that you know about the process by which food is converted into energy and some of the various hormones and processes involved, it’s time to look at the factors that affect the efficiency of that process. Metabolism actually refers to the way—not the speed—in which your body processes and uses the food you eat each day. The idea of a faster or slower metabolism is not really as accurate as the idea of an efficient, dysfunctional, or inefficient metabolism.
Metabolism itself is made up of several components:
The essential formula is that input should equal output.
|
INPUT |
OUTPUT |
|
Calories from food = |
Calories expended from basal metabolism + Calories expended by activity + Calories expended digesting food (thermic effect) |
Many overweight people do not eat any more than people of average weight. So it’s clear that the problem for many must be on the output side of the equation. In most overweight people, either basal metabolism is lower, activity is less, and/or the thermic effect of food is blunted. Bottom line: overweight people just don’t burn as many calories as people of normal weight.
METABOLIC EFFICIENCY
The efficiency of your metabolism is affected by a number of factors.
Body Composition/Muscle Versus Fat
Muscle cells are as much as eight times more metabolically active than fat cells. So the greater the proportion of muscle to fat, the more efficient your metabolism is at burning fat. Ric Rooney and Bart Hanks of the Physique Transformation Web site say that a pound of muscle costs up to 50 calories a day to maintain, and a pound of fat costs just 2. One study actually found that lifting weights boosted the resting metabolic rate by 9% over 18 weeks by adding 4 pounds of muscle mass. By the time 2 pounds of muscle is gained—usually over 3 months or so—your extra muscle can burn as much as an extra 65 calories a day.
The amount of weight-bearing exercise you do has an effect on your metabolism. Building muscle mass usually requires some sort of weight-bearing or resistance work such as lifting weights, using exercise bands or hand weights, and other similar forms of exercise.
Brown Fat
According to Stephen Langer, an expert on weight loss and thyroid function, one lesser-known aspect of metabolism is brown fat, also known as brown adipose tissue (BAT). BAT is a special kind of adipose fat that collects below the neck and extends down the back. It helps convert deposits of body fat into heat. The hypothalamus helps your nervous system trigger the action of brown fat, whose specialized mitochondria are particularly effective at generating heat and energy. People who are overweight may have lost the assistance of brown fat, and their excess calories go into fat storage.
Aerobic Exercise
Aerobic exercise, which increases heart rate, will also raise metabolism while you’re exercising. And some experts believe that aerobic exercise boosts your resting metabolism for several hours afterward, as your muscles burn calories to recover and repair themselves.
Food Intake
Metabolism is affected by how much you eat. When you are eating an insufficient amount of calories, your body perceives itself to be in starvation mode and will start to cannibalize your own muscle, burning it off for fuel. It will hold on to fat as protection. In his book Turn Up the Heat, Philip L. Goglia talks about the impact of a too-low-calorie diet on weight problems.
I have found that most of the people who come to me with weight and health problems are usually already ingesting far fewer calories than they should in order to efficiently fuel their bodies. Therefore, their metabolism, the body’s calorie-burning furnace, is already running 25 percent to 60 percent below its ideal metabolic-efficiency level. In turn, the body is storing much of the limited amounts of food these individuals eat as fat and wasting muscle tissue as an adaptive mechanism to create an alternative energy source.
At the same time, eating more food increases metabolism. One study found that as calorie intake increases, there is a corresponding increase in metabolic efficiency that is designed to maintain you around a particular body weight. However, if your caloric intake exceeds your body’s ability to burn up those calories over time, the excess calories are converted into fat and glucose.
The Type of Food You Eat
Protein requires more energy to be broken down, digested, and absorbed, and resting metabolic rate typically goes up after eating protein as much as two to three times more than after eating carbohydrates and fats.
Your Age
The body typically starts to lose muscle after age 30, so everything else being equal—activity level, calorie intake—you’ll gain weight because of this loss of muscle.
Genetics
Some people simply have a naturally more efficient metabolism than others.
Nutritional Status
Metabolism requires the smooth running of many complex physiological processes. When there are nutritional deficiencies, particularly in antioxidant vitamins such as B and C, metabolism can become less efficient.
Water Intake/Hydration
When the body has taken in sufficient water, body temperature can be maintained for optimal metabolism. Dehydration can make the body temperature drop slightly, and with a reduction in temperature, the body will attempt to help raise temperature by storing fat to act as an insulator. So drinking too little water can contribute to an inefficient metabolism and hoarding of fat.
Menopausal Status
Menopause also adds additional hormonal burdens to metabolism and weight loss. During menopause, women become more effective at storing fat and less able to burn fat. After menopause, an enzyme called adipose tissue lipoprotein lipase (AT-LPL) is more active. AT-LPL breaks fat down so that fat cells can absorb it. One study found that the burning ability of fat taken from the buttocks of postmenopausal women was 75% less than in perimenopausal women.
Summary
As you can see, the body is a calorie miser, and there are a number of places that these complicated processes can fail, making it easier for you, especially as a thyroid patient, to gain weight, and making it harder to lose weight.
The next chapter expands upon this understanding to explore the linkages between your thyroid, metabolism, and weight-loss efforts.