Important clues about the individual nature of weight loss come from the National Weight Control Registry. This is a select “club” of more than 10,000 women and men who lost an average of 30 pounds and kept it off at least a year. What’s their secret? They don’t have one.29 An early look at registry participants showed that:
• 45 percent said they lost weight on their own; the others relied on some type of program. Interestingly, this is similar to the experience of those who quit smoking: most do it on their own by going cold turkey, presumably motivated by the accumulation of information about the dangers of continuing to smoke.
• 98 percent changed what they ate in some way, usually by cutting back on daily calories.
• 94 percent exercised more, usually by walking.
One of the main messages from the registry is that successful weight loss is very much a “do it your way” endeavor.
Consumer Reports once surveyed more than 32,000 dieters. Its findings echoed the findings from the registry. Nearly one-quarter of those surveyed lost at least 10 percent of their starting body weight and kept it off for at least a year. Most chalked up their success to eating less and exercising more.30 The vast majority did it on their own, without resorting to commercial weight-loss programs or weight-loss drugs. Interestingly, the successful dieters in the Consumer Reports survey tended to adopt low-carb, high-protein rather than low-fat diets.
What the registry and Consumer Reports groups have in common is a focus on daily calories and exercise. In other words, successful dieters learn to manipulate energy in and energy out to lose or maintain weight.
A second thread of truly scientific evidence about dieting comes from randomized controlled trials like DIRECT (see page 56) and others. As I mentioned earlier, these are the gold standard of medical research. Such trials have shown that people who follow low-carb or Mediterranean diets tend to lose weight faster than those who follow low-fat diets. Interestingly, although some low-carb dieters who consume large amounts of meat and high-fat dairy foods have increases in harmful LDL cholesterol, low-carb dieters generally have larger reductions in potentially harmful triglycerides and increases in protective HDL cholesterol than low-fat dieters. The best long-term outcomes, both for weight and cholesterol and other metabolic variables, have been with the Mediterranean-type diet.
To see if we could learn more about the effectiveness of low-fat and higher-fat diets, several of my colleagues and I evaluated fifty-three randomized clinical trials that compared the impact of low-fat and higher-fat diets for at least a year. When the intensity of counseling and monitoring was the same in both diets, higher-fat, lower-carbohydrate diets helped people lose weight slightly more than low-fat diets did.31
But buried in the data from these trials is the finding that people respond differently to different diets. For some people, low-carb diets work well. For others, low-fat diets are the ticket. There’s an important lesson here: It’s okay to experiment on yourself. If you give a particular diet your best shot and it doesn’t work after a few months, it’s possible that it isn’t the right one for you, your metabolism, and/or your situation. Don’t get too discouraged or beat yourself up because a diet that “worked for everybody” didn’t pay off for you. Try another. You’ll do all of your body good if it is based on foods that deliver healthy fats, carbohydrates, and protein packages—precisely what the Harvard Healthy Eating Pyramid and Healthy Eating Plate recommend.
DO IT YOURSELF
Instead of following someone else’s weight-loss diet, build your own. Base it on a Mediterranean-type diet, which is the one that works best for long-term weight control and overall good health. With the information provided in this book, you can swap in or out the basic elements of the traditional Mediterranean diet to incorporate the foods and flavors of other cuisines and cultures, including your own personal tastes.
A good diet should provide plenty of choices, relatively few restrictions, and no long lists of sometimes expensive special foods and supplements. It should be as good for your heart, bones, brain, and colon as it is for your waistline. And it should be something you can sustain for years.
The principles of healthy eating presented in this book can give you the foundation for such a plan. They won’t give you a quick fix. Instead, they offer something better: a lifetime of savory, healthy choices that will be good for all of you, not just parts of you.
CHAPTER FIVE
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Straight Talk About Fat
FEW PUBLIC HEALTH MESSAGES HAVE been as powerful and as persistent as the false “Fat is bad” message that has dominated talk about the American diet for decades. Beginning in the 1970s, fat became dietary Public Enemy Number One, feared for its ability to cause disease and even kill. As a nation, we took that message to heart. The average American now eats a lower percentage of calories from fat than he or she ate four decades ago. We spend billions of dollars a year on low-fat cookies, no-fat salad dressing, pills that block the absorption of fat from the digestive system, and all manner of fat-busting diets and cookbooks.
But we aren’t any healthier for it. In fact, we’re worse off in many ways. An astounding two-thirds of adult Americans are overweight. And more than half of those are classified as obese.1 The number of people with diabetes has greatly increased over this period. And the war on fat hasn’t appreciably reduced rates of heart disease and obesity-related cancers—the two main reasons for it in the first place.
Fast Fact: Putting Fats to Work
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Your body depends on fats for a host of functions. They are a major energy source for cells. They make up body fat (adipose tissue), which stores energy, cushions and protects vital organs, and provides insulation. Many people think of cholesterol as a fat, but it isn’t, because it is made up of rings of carbon and hydrogen atoms, not simple chains (see “Types of Fat” on page 76). The body doesn’t break down cholesterol for energy but instead uses it to make cell membranes, the critically important sheaths around nerves. It is also a building block from which the body makes vitamin D and many hormones.
Before exploring the health effects of dietary fat on health, let’s take a look at the varieties of this important component of food.
What went wrong? The war on dietary fat ignored the simple fact that your body needs fat (see “Fast Fact: Putting Fats to Work,” page 75). Some types are essential for you, and it’s important to include them in your diet. These are the healthy unsaturated fats found in plant oils like olive, canola, soybean, and corn oils, and in fish. Cutting them from your diet is a bad idea. The true bad fats are trans and saturated fats. Trans fats, produced by the industrial process of partial hydrogenation, shouldn’t be part of anyone’s diet (see page 83). Saturated fat, from red meat, dairy foods and tropical oils, is better off being replaced with unsaturated fats whenever reasonably possible.
TYPES OF FAT
Chemically speaking, the family of fatty acids—the true and technical term for what most people just call fats—is part of the extended clan known as lipids. All members of the fatty acid family consist of a chain of carbon atoms bonded to hydrogen atoms with maybe a smattering of oxygen atoms. That’s it—no nitrogen, iron, or other elements. What makes one fatty acid different from another is the number of carbon atoms, how the carbon atoms are connected to each other, and the geometry of the carbon chain.
Types of Dietary Fat
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Type of Fat
Important Sources
State at Room Temperature
Effect on Cholesterol Compared with Carbohydrates
Monounsaturated
Olives and olive oil, canola oil, peanut oil; cashews, almonds, peanuts, and most other nuts; peanut butter; avocados
Liquid
Lowers LDL; raises HDL
Polyunsaturated
Corn, soybean, safflower, and cottonseed oils; fish
Liquid
Lowers LDL; raises HDL
Saturated
>
Whole milk, butter, cheese, and ice cream; red meat; chocolate; coconuts, coconut milk, and coconut oil
Solid
Raises both LDL and HDL
Trans
Most margarines; vegetable shortening; partially hydrogenated vegetable oil; deep-fried fast foods; most commercial baked goods
Solid or semi-solid
Raises LDL*
* Compared to monounsaturated or polyunsaturated fat, trans fat increases LDL, decreases HDL, and increases triglycerides.
Fats and Cholesterol in the Bloodstream
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For fats to get from your digestive system to the cells that need them, they must travel through your bloodstream. That isn’t as simple as it sounds. Like oil and water, fats and blood don’t mix. If your intestines or liver simply dumped digested fats into your blood, they would congeal into unusable globs. Instead, fat is packaged into protein-covered particles that mix easily with blood and flow with it. These tiny particles are called lipoproteins (lipid plus protein). During the packaging process, the body adds some cholesterol for delivery to cells and to help stabilize the particles.
Like a highway at rush hour, your bloodstream carries many sizes and shapes of fat-transporting particles. Lipoproteins are generally classified by the balance of fat and protein they contain. Those with a little fat and a lot of protein are heavier and more dense; those that contain more fat than protein are lighter, fluffier, and less dense. The proteins do more than help fat mix with blood. Those on the outside of the particles act like address labels that help the body route fat-filled particles to specific destinations. Once there, cells pull fats and cholesterol from the particles to use as energy or building blocks.
Cholesterol Testing
When you have your cholesterol checked, you usually get back several test results. Total cholesterol tells you how much LDL, HDL, and other lipoprotein particles are circulating in your blood. The ideal total cholesterol level is under 200 milligrams per deciliter (one-tenth of a liter) of blood. Borderline high cholesterol is a total cholesterol level between 200 and 239 milligrams per deciliter and high cholesterol is 240 milligrams per deciliter or higher.
Because total cholesterol is a mix of bad and good, it doesn’t tell the whole story about what’s happening in your bloodstream, arteries, and other tissues. That’s why many physicians also check LDL and HDL levels. The lower the LDL the better, with anything under 130 milligrams per deciliter considered healthy. A level between 130 and 159 milligrams per deciliter is borderline high, and 160 milligrams per deciliter or above is high. For people with heart disease or at high risk for it, the thresholds are lower. The opposite is true for HDL: higher levels offer greater protection against heart disease. An HDL over 35 milligrams per deciliter is considered okay, although higher is better.
The exact role that triglycerides play in the development of heart disease is controversial, but recent studies show that a high level of them increases the odds of developing it. A normal triglyceride level is below 150 milligrams per deciliter. Borderline high is between 150 and 199, and high is anything above 200 milligrams per deciliter.
Almost all of the fatty acids in our diet are triglycerides: three fatty acids bound together by a “glue” called glycerol. There are four main categories of these: saturated, monounsaturated, polyunsaturated, and trans (see “Types of Dietary Fat” on page 76). From here on out I will refer to fatty acids simply as fats, which is how they are listed on food labels.
Until the middle of the twentieth century, fats were thought to play one main role in the body: serving as fuel for cells. We now know that they have many other important jobs. Fats provide the raw materials for building cell membranes, the delicate yet sturdy skin that surrounds cells and controls what gets in and what gets out. Fats make up the sheaths that surround and protect nerves. They provide raw materials that the body uses to make hormones and the chemicals that control blood clotting and muscle contraction.
The human body can build most of the different fats it needs from any other fat in the diet. If your body needs more of one type of monounsaturated fat for a specific function, it can make it out of saturated fat. It can also build fat from carbohydrates. However, a few fats can’t be made from scratch. Called essential fats, these must come directly from food.
Here is a quick overview of the types of fat in food, and how they affect the body.
Saturated fat. The term “saturated” means that the carbon atoms in a chain hold the maximum number of hydrogen atoms they possibly can. This happens only when each carbon atom is connected to its carbon neighbors by single bonds. Saturated fats look like straight chains.
About two dozen different saturated fats exist in nature. They are abundant in meat and animal fat, milk and dairy foods, and a few vegetable oils like palm and coconut oil. At room temperature, saturated fats are solid rather than liquid, something you see if you let the drippings from cooked bacon or hamburger congeal in a pan.
When it comes to their effects on cholesterol and the artery-clogging process known as atherosclerosis, saturated fats come in gradations of bad. The saturated fats in butter and other dairy foods strongly increase harmful LDL cholesterol (see “Cholesterol Types and the Heart” on page 79). Those in beef fat aren’t quite as powerful at boosting LDL, and those in chocolate and cocoa butter have an even smaller impact. The saturated fats in coconut oil give an extra boost to protective HDL. That has given a halo to this source of fat, which is often touted as being a wonder food for the heart, the skin, and more. But any HDL boost from coconut oil doesn’t compensate for its LDL-raising effect.
Fast Fact: Cholesterol Types and the Heart
* * *
Cholesterol moves through the bloodstream packaged in tiny particles called lipoproteins. The three key types, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and very-low-density lipoprotein (VLDL), have the biggest effects on heart health.
LDL is often referred to as “bad” cholesterol. When there are too many LDL particles in circulation, they can build up inside of artery walls. This narrowing of the artery, called atherosclerosis, makes it difficult for blood to flow through the vessel. These cholesterol-laden buildups, called plaque, set the stage for heart attacks and strokes.
In contrast, HDL is often referred to as “good” cholesterol. These particles sponge up cholesterol from the bloodstream, the lining of blood vessels, LDL and VLDL particles, and elsewhere. They carry it to the liver for disposal. HDL also helps the liver recycle other lipoprotein particles.
Triglycerides make up most of the fat that you eat and most of the fat that circulates in your bloodstream. Triglycerides are essential for good health, since your tissues rely on them for energy. But, as is the case for cholesterol, too many triglycerides in circulation may be bad for the arteries and the heart.
Monounsaturated fat. The Greek prefix mono-, meaning one, hints at the structure of these fats. At one point along the carbon backbone, two carbons are connected by a double bond. This seemingly small change in structure leads to three key differences. It reduces the number of hydrogen atoms the carbon chain can hold by two. It changes the shape of the molecule from a straight chain to a bent stick. And it makes the fat a liquid at room temperature. Monounsaturated fats are the primary fat in plant oils, including olive oil, peanut oil, and canola oil. Avocados and most nuts are also good sources of this healthful fat. When eaten in place of carbohydrates or saturated fat, monounsaturated fats reduce harmful LDL.
Polyunsaturated fat. A fat with two or more double bonds is a polyunsaturated fat. A polyunsaturated fat holds even fewer hydrogen atoms than a monounsaturated fat with the same number of carbon atoms. Magnified thousands of times, a polyunsaturated fat would look like a stick with two or more bends. Polyunsaturated fats are also liquid at room temperature. Polyunsaturated fats can be subdivided into the omega-3 and omega-6 groups. (“Omega” means end, and the number refers to whether the double bond is between the th
ird and fourth carbon from the end of the chain or the sixth and seventh.) Each type plays different roles in the body. Our bodies don’t make polyunsaturated fats, so we need to get these essential fats from eating plant oils like corn and soybean oil, seeds, whole grains, and fatty fish such as sardines, salmon, and tuna. Like monounsaturated fats, eating polyunsaturated fats in place of carbohydrates or saturated fat reduces harmful LDL. They are needed for cell growth, brain function, and proper functioning of the immune system, and also help the heart keep a steady rhythm.
Trans fats. More than one hundred years ago, food chemists discovered that they could solidify polyunsaturated vegetable oil by heating it in the presence of hydrogen gas and finely ground particles of nickel. During the process, called partial hydrogenation, hydrogen latches on to some—but not all—of the double-bonded carbons, changing them into single bonds. At the same time some of the remaining double bonds twist into a new straightened shape, which gives the fat new chemical and physical properties.
Why did anyone bother? It turns out that it’s easier to ship and store solidified vegetable oil than liquid oil. Partially hydrogenated vegetable oil can be used in place of butter or lard in baking. A lesser degree of hydrogenation yields a still-liquid oil that doesn’t become rancid as quickly as unprocessed vegetable oils. Without hydrogenation, we wouldn’t have had margarine or vegetable shortenings such as Crisco. We’d also have less heart disease and thousands of fewer deaths from it each year (see “Trans Fats—A Special Concern” on page 83).
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