Some people store much of their fat around the waist and chest, others store it around the hips and thighs. These two diﬀerent body shapes have been dubbed apple and pear. Magazine articles and Web sites make a big fuss out of these arbitrary categories, and several Web sites use your waist and hip measurements to calculate your waist-to-hip ratio, then use it as a key point in determining your health proﬁle and risk of developing heart disease.
Fat that accumulates around the waist and chest (technically called abdominal adiposity) may pose more of a health problem than fat around the hips and thighs. Abdominal fat has been linked with high blood pressure, high cholesterol, high blood sugar, and heart disease. It is possible that this fat is metabolically more active than fat stored elsewhere. It is also possible that it isn’t any worse than other kinds of fat but instead is a way of telling us about overall fatness that weight and height alone can’t describe.
Where, exactly, is your waist? For clothing designers, it’s the narrowest part of the torso. For scientists studying the health eﬀects of body fat, it’s the region near the navel, where fat is typically deposited. In large standardized health surveys, such as the ongoing National Health and Nutrition Examination Survey, researchers use a two-step process to measure a volunteer’s waist: One, gently press the right hipbone to ﬁnd its high point. Two, place the tape measure just above that point and extend the tape around the abdomen, keeping it parallel to the ﬂoor. For most people, the top of the hipbone is generally in line with the navel. Others may need to pull the tape down a bit to the top of the hipbone.
The waist measure can be useful because many people— particularly men—ﬁnd themselves converting their muscle to abdominal fat as they go through midlife. Even though weight may remain stable, an expanding waistline can be a warning sign of trouble on the horizon. So use your waist as a kind of low-tech biofeedback device—a waistwise expansion of two or three inches over the years should trigger a warning that you need to reevaluate your diet and physical activity level. Some researchers advocate calculating a waist-hip ratio (dividing the size of your waist by the size of your hips). Simply measuring your waist is probably just as useful. Many studies have shown that this single number is just as powerful at gauging the chances of developing chronic disease as the waist-to-hip ratio. It’s also a lot easier to do.
A CALORIE IS A CALORIE IS A CALORIE
We eat food for two physiologic reasons, energy and chemical building blocks. The amount of energy a particular food can deliver to mitochondria—the tiny engines that power your cells—is measured in calories. Technically, a food calorie is the amount of heat needed to raise the temperature of a liter of water (just over a quart) from 14.5° C to 15.5° C. Practically, a food calorie is the amount of energy a 150- pound person burns each minute while sleeping.
If you read diet books or keep up with health and nutrition news, you’ve probably heard a lot about “fat calories” or “carbohydrate calories.” The idea that fat calories are diﬀerent from carbohydrate calories came from studies done under extreme conditions, such as consuming pure carbohydrate, protein, or fat. In these situations, the body converts dietary fat to body fat a bit more eﬃciently than it does carbohydrate or protein.
In a normal diet, though, your body converts all three to fat at the same rate. Like a kiss or a rose, a calorie is a calorie. So ﬁve hundred calories from ice cream, ﬁve hundred from red meat, and ﬁve hundred from pasta will have similar eﬀects on your weight.
This calorie blindness is the result of a neat solution to a vexing problem faced by some of earth’s early inhabitants— how to run a body on diﬀerent fuels. Instead of having completely diﬀerent intracellular systems for fats, carbohydrates, protein, and alcohol, the cells in your body use the same energy source. Much of what you eat is (or can be if needed) converted to the energy coin of the realm, a six- carbon sugar called glucose. When you eat, some of the glucose dumped into your bloodstream is used immediately by your cells. Some is linked into long chains, called glycogen, and stored in your muscles and liver. Any leftovers are converted to fat and squirreled away in special fat storage cells and padded in between muscles. If glucose is like cash in your pocket, ready to be spent when needed, glycogen is money in the bank, available with a bit of eﬀort, and fat is money tied up in stocks or mutual funds.
Does Fiddling with the Form of Calories Help You Lose Weight?
Almost any kind of diet can lead to weight loss, at least for a few months. Some of the most absurd diets ever published have their champions who will testify, complete with eight- by-ten glossy color photographs, that the diet helped them lose weight. That’s because even the oddest diet makes people pay attention to how much they are eating, rather than eating willy-nilly throughout the day. This mindfulness is often enough to limit daily calories, the single most important key to controlling weight. It is aided and abetted by the monotony imposed by many of these diets and their inability to please the palate. Most fad diets fail in the long run. For that matter, so do most middle-of-the-road, commonsense diets.
Diets usually vary in the way they deliver calories. Although a calorie is a calorie, how you get yours may make a diﬀerence in limiting your daily intake. The ultimate diet would be one that oﬀers meals and snacks that rapidly lead to feeling pleasantly full (technically called satiety), delay the return of hunger pangs (technically called satiation), are pleasing and satisfying, meet the body’s needs for energy and nutrients, and work to prevent chronic disease. That’s a tall order. Countless books have been written claiming they’ll give you all or part of this dietary nirvana. Most promise far more than they deliver.
Diets usually ﬁddle with the form of calories by focusing on one particular dietary villain or hero. The most common include low-fat, low-carbohydrate/ high-protein, the glycemic index, and energy-density strategies.
learn more: Eat, Drink, and Be Healthy!
LOW-FAT DIETS AREN’T THE ANSWER
A common, though incorrect, thread that runs through many diets is the idea that fat in food makes fat in the body. Limit “fat calories,” so the thinking goes, and you’ll be able to control your weight. Although there’s a pleasant symmetry to the logic, and although many dietary guidelines focus on reducing dietary fat, there’s no good evidence linking dietary fat with excess weight. In fact, there’s plenty of evidence showing that the percentage of calories from fat has little to do with excess weight. That’s why the Healthy Eating Pyramid doesn’t ban fats across the board. Instead, it treats fats as one of the most important nutritional factors in your diet. What fats to choose and how much to eat are discussed in chapter 4.
To be sure, some countries with high fat intake have many
overweight people. In the United States, for example, the average person gets about one-third of his or her daily calories from fat (a relatively high percentage), and almost two-thirds of the population is overweight. But in some parts of South Africa, where 60 percent of people are overweight, fat contributes barely one-quarter of calories.
I am not trying to absolve dietary fat or downplay its contributions to weight or weight gain. Dietary fat has an impact on energy, fat stores, and weight. But if you balance the number of calories you eat with the number of calories you burn, especially if part of the burn comes from exercise, then you won’t gain weight on a diet that has 35 or even 40 percent of calories from fat. And if you are eating the right kinds of fat, you will help protect yourself from heart disease and other chronic conditions.
learn more: Building a Better Pyramid
LOW-CARBOHYDRATE DIETS MAY HELP
For almost thirty years, mainstream nutrition experts dismissed Dr. Robert Atkins’s carbohydrate-shunning diets as an unhealthy fad. How in the world could a high-protein, high-fat, low-carbohydrate diet help with weight loss, the medical establishment reasoned, when everyone knew that fat was the dietary demon? Now that the Atkins diet is getting its day in court—the court of careful scientiﬁc testing
—the good doctor appears to have been about half-right.
Limiting carbs and loading up on meat, cheese, and eggs gives the digestive system more work to do, and this may help you feel full longer. And by smoothing out the blood sugar/insulin roller coaster (see “Why Carbohydrates Matter” in chapter 5), it may stretch the time between hunger pangs. But eating unlimited amounts of beef, sausage, butter, and cheese—as promoted by the original Atkins diet—is a bad idea for overall optimal health. There are healthier ways to cut back on carbs. Following the Healthy Eating Pyramid and eating more ﬁsh, poultry, beans, nuts, fruits and vegetables, whole grains, and vegetable oils can work for weight control even as it reduces the risks of heart disease, diabetes, and several cancers. Even Atkins seems to have been heading in that direction before his untimely death in 2003, as his ﬁnal book had shifted toward this version of a low-carbohydrate diet.
LOW-ENERGY-DENSITY DIETS MAY BE CONFUSING
When it comes to gaining or losing weight, is there any diﬀerence between eating a baked potato or a cookie that delivers the same number of calories? Several popular diet books say there is. They focus on energy density (sometimes called caloric density) as a key to controlling weight. The thinking here is that foods that deliver relatively few calories per bite, like soup or baked squash, ﬁll you up faster than foods that pack more calories per bite, like meat or nuts. The faster you feel full with fewer calories, so the thinking goes, the less you will eat.
Calculating energy density is simple. You divide the
number of calories in a particular food by its weight in ounces or grams. Apples, potatoes, cooked rice, and lettuce have low energy densities, largely because they are mostly water. Nuts, bagels, and cookies have high energy densities.
If people eat similar weights or volumes of food, no matter what the energy density, reducing the energy density decreases calorie intake. Pure fat has a relatively high energy density (nine calories per gram) compared with pure protein and carbohydrate (four calories per gram). Short-term successes with the energy density approach to weight loss have been used to champion the importance of low-fat diets. But we don’t eat pure carbohydrates or pure fats—we eat mixtures of these. A salad with oil-and-vinegar dressing, or roasted vegetables sprinkled with olive oil, have low energy densities but high percentages of calories from fat. Likewise, many fat-free products have the same energy densities as their full-fat versions because the fat has been replaced with highly reﬁned carbohydrates.