Bring Your Fat to a Checkup

Your weight, BMI, and body-fat percentage provide some important clues about your overall health, but they’re far from definitive. For more comprehensive information, it’s time to doctor up.

Yes, you may hate waiting in the doctor’s office. And you probably aren’t crazy about stripping off your clothes and donning a paper gown that’s roughly the width of two paper towels. But your family doctor is an important team player in every aspect of your body’s health. If your weight has been creeping up and you’re starting to get nervous about the possible ill effects, your doctor can run some of the following tests:

• Cholesterol levels. Doctors measure two types of cholesterol. At high levels, LDL cholesterol can clog your arteries when it forms into a sticky plaque. HDL cholesterol is the good stuff—it helps mop up excess LDL cholesterol, keeping your arteries clean. To stay healthy, you need a balance between these two players. A blood test can tell you how your body is doing.

• Triglyceride level. Triglycerides are a form of fat that travels through your bloodstream. Your body uses triglycerides to move fat from one spot to another, so it can fuel the work going on in your body. But if there’s too much fat circulating in your blood, you’re at greater risk for heart disease. Once again, you can check your triglycerides with a blood test.

• High blood glucose. Normally, the human body is extremely effective at pulling excess sugar out of your blood using insulin. But if this sugar-storage system is starting to malfunction—perhaps after a lifetime on the Krispy Kreme diet—your blood will stay sugared-up. This is the beginning of diabetes. Left unchecked, the runaway sugar can damage your heart, eyes, and kidneys.

• Blood pressure. Blood pressure measures the force of your blood as it pushes through your arteries (page 161). Although high blood pressure causes no immediate damage (and has virtually no obvious symptoms), over time it strains your heart and thickens your arteries. Left untreated, it can lead to organ damage, heart attack, or stroke.

Even if you have an ideal BMI and aren’t worrying about your weight, there are reasons you might still want to take these tests. For example, you might have a family history of early heart disease, smoke two fistfuls of cigarettes between breakfast and lunch, or have unexplained symptoms. If in doubt, chat it up at your next physical.

Source of Information : Oreilly - Your Body Missing Manual

Do-It-Yourself Fat Measurement

A body-fat scale (which looks like your average bathroom scale, but measures electric conductance instead of weight) is the most affordable, practical way for you to keep an eye on your fat without getting help from someone else. But even top-rated scales make so many assumptions that you can’t trust the number they give you. So does that make them a gargantuan waste of time?

Not necessarily—provided you use your body-fat scale to measure changes in body fat.
Used this way, a body-fat scale lets you judge the success of an exercise plan or the toll of an expanding waistline. To use this strategy, you need to make sure you get a consistent reading. Here are some tips that can help:

• Watch your water intake. The amount of water in your body can dramatically change the reading of a body-fat scale. The best idea is to measure your body fat at the same time of day, at least one hour after drinking or eating, and definitely not after exercise. Consider making it part of your morning routine.

• Adjust the settings. For example, many scales have a specific profile for athletes or children. If you pick the right settings, the scale is more likely to make the right assumptions for your body and give you a more accurate reading.

• Don’t compare people. You and your friend may use the same scale, but it’s not fair to compare the numbers. Minor differences between the two of you can skew the results in different ways. Similarly, it doesn’t make sense to compare your own readings on different body-fat scales.

• Get a baseline. If you get the chance, measure your body fat with a more reliable method—for example, a skinfold test or an underwater weighing—then compare that result with the reading on your scale to figure out a basic frame of reference for how accurate your scale is.

Source of Information : Oreilly - Your Body Missing Manual

Body-Fat Percentage

If you’re concerned about good health, your sheer poundage isn’t nearly as important as finding out how much of you is made up of fat. In other words, you need to spend less time thinking about your weight and BMI, and more time concentrating on your body-fat percentage—the weight of your fat compared to the total weight of your body.

Everyone has a certain amount of essential fat stored in small amounts in organs, bone marrow, muscles, and the nervous system. This fat supports the normal functioning of these systems. Women have a bit more fat in the breast, pelvis, hips, and thighs, which is a prerequisite to making babies. Along with this bare minimum, it’s important to have at least a little more fat to use as an energy reserve, so you don’t collapse the next time you skip breakfast.

Unfortunately, the only place you can get a foolproof measure of your body-fat percentage is on an autopsy table. Some other techniques are nearly as good, but require the work of professionals and expensive hospital equipment. A few are much less accurate, but can be carried out at home. Here’s a quick roundup of the ways to measure your body fat:

• Imaging. An MRI (magnetic resonance imaging) machine can peer under your skin to create shocking scans that show the amount and distribution of your body fat.

• Hydrostatic weighing. Some specialized laboratories (and a few health clubs) have water tanks that are designed for underwater weighing. This technique works because fat isn’t nearly as dense as muscle and bone (which is why well-padded people float more easily). Using a bit of math, you can combine your underwater weight with your normal weight to get a fairly accurate measurement of your body-fat percentage.

• Skinfold measurements. To perform this test, a professional painstakingly pinches the folds of fat in various places on your body using calipers. It’s not particularly accurate, and it doesn’t sound like anybody’s idea of a fun Friday night. However, it works well if you just want to monitor changes in your body fat, as long as you get the same person to administer the measurement each time.

• Electrical conductance. This test sends a faint current through your body, calculates your body’s electrical resistance, and uses the result to estimate your body-fat percentage. This works because muscle contains a lot of water, and so conducts electricity quite well, while fat does not. This technique is used in hospital-grade equipment that costs tens of thousands of dollars, and in cheapie department-store versions, which look like ordinary digital scales.

Source of Information : Oreilly - Your Body Missing Manual

Body Mass Index

One common, but somewhat crude, measure for assessing your poundage is the body mass index, or BMI. Oddly enough, the BMI was created by a Belgian mathematician (perhaps concerned about overindulging on the chocolate delicacies of his countrymen). In any case, the BMI became a surprisingly popular and somewhat controversial way to separate the thin from the fat. To calculate your BMI, you divide your height (in meters) by your weight (in kilograms). Or, you can plug more common pound and inch measurements into this version of the formula:

BMI = weight (lb) * 703 / ( (height * height) (in * in) )
This gives you a single number that ranks your weight. For example,
if you’re five feet eight inches tall (that’s 68 inches total) and weigh 180
pounds, your BMI is 27.4. According to the standard BMI groupings, that
puts you into the overweight category.

If you don’t want to pull out your pocket calculator, you can use one of the many BMI calculators online (just search for “BMI”). Or you can find your spot on the handy BMI chart shown, which helps you judge exactly where you fall in your weight class.

The BMI has some known weak spots. For instance, short, muscular types and athletes can end up in the obese zone even though they’re in prime condition. Similarly, elderly folks can coast through with a normal ranking if they have high body fat combined with very little muscle weight.


Despite these weaknesses, the BMI is good for two things:

• Making conclusions about a population. For example, if the BMI suggests that one-third of Americans are dangerously obese (as it does), the odds are that very few of them are muscular athletes in the prime of their lives.

• Giving a rough idea of the weight situation for an ordinary person. If you fall far outside the normal zone, the BMI is giving you a red warning flag. It’s up to you to follow up and see if you really do have the weight problem it suggests. The standard next step is to measure your waist and analyze your blood.

Source of Information : Oreilly - Your Body Missing Manual (08-2009)

The Lessons of Fat Cells

Finding out the secret rules of fat cells is fascinating, but does it do you any good? The obvious hope (both for failed dieters and pharmaceutical executives) is that this understanding will lead to a drug that can control appetite or fat storage. In the meantime, you can learn a few things from your fat cells:

• Hold the line on childhood eating. No one knows why different people gain different numbers of fat cells throughout childhood and adolescence. However, there’s at least a possibility that environmental influences are at work, meaning early binging habits might tune the body to a lifetime of calorie craving. So if you’re a parent, make every effort to provide a varied, healthy diet for your child—one that’s rich in fruits and vegetables, and low in processed foods—and resist the temptation to teach “clean your plate” or “food is your reward” lessons. Even if your efforts don’t influence your child’s fat cell count, they’ll help set down lifetime habits that can defend against the worst dietary excesses.

• Expect diets to be difficult. Because a diet can’t change your fat-cell count, you’ll always have the potential to regain the weight you lose. To give yourself the best odds of staying slim, start by dieting small (with a goal of losing 10 pounds at a time), then concentrate on maintaining your weight and adjusting to a new lifestyle.

• Don’t moralize fat. While it’s a biological fact that fat people get fat by eating too much, none of us is completely in control of the powerful drive to eat. Those with a larger collection of fat cells just might start life with the odds stacked against them.

Source of Information : Oreilly - Your Body Missing Manual (08-2009)

The Life and Death of a Fat Cell

As you’ve seen, fat cells are like miniature people—the more fat you feed them, the more they plump up. Unfortunately, even the strictest diet can’t remove them. Instead, it leaves you with billions of slimmed-down fat cells crying out for another meal.

But there’s another side to this story. Different people do have different numbers of fat cells. Not only do obese people have dramatically bigger fat cells than slim people, they often have many more. For years, scientists have wondered what causes these differences. Do fat cells ever die? Does something trigger the creation of new fat cells? Is it our fault?

In 2008, a group of scientists devised a clever experiment to answer these questions. It worked by examining the effect of nuclear-bomb explosions on human fat cells. At first glance, this sounds like a Very Bad Idea. After all, detonating nuclear bombs— even in the name of science—is likely to put off the ethics board. But here’s the trick: the researchers didn’t launch the bombs themselves. Rather, they took advantage of a bit of Cold War history to track radioactive carbon in human fat cells.

Now you’re probably wondering what radioactive carbon is doing in human fat cells, and that’s a reasonable question. The obvious answer is“because the researchers put it there,” but it turns out they aren’t allowed to do that, either. (It’s likely to be toxic.) The experiment was launched, unknowingly, by the American and Soviet militaries when they tested nuclear bombs. These tests sent large amounts of radioactive carbon into the atmosphere that drifted to all corners of the world. Plants pulled it out of the atmosphere, animals ate the plants, and we ate the animals. The end result is that the U.S. and Soviet governments radioactively labeled pretty much everyone who was around at the time.

Here’s a chart that shows how the levels of radioactive carbon soared during nuclear testing and rapidly diminished when nuclear testing went underground in 1963.

By matching the level of radioactive carbon in the air with the amount of it in the DNA of a fat cell (along with a generous pinch of statistical mojo), researchers can figure out when that cell was created. It’s as though each fat cell has its own “manufactured on” date.

To draw their conclusions, the researchers analyzed fat extracted from about 700 people. Here’s what they found:

• The number of fat cells grows through childhood and adolescence, but stabilizes sometime in late adolescence. After that, your fat-cell count stays the same.

• People on the fast track to obesity pack on their fat cells more quickly in childhood and stop producing them around age 16 or 17. Naturally thin people have fewer fat cells, but keep producing them until the age of 18 or 19.

• Even extreme events—for example, dramatic weight loss through surgery or super-sized weight gain—change the size of fat cells in the body, but don’t nudge the number. (That said, many experts believe years of excessive weight gain that lead to hundreds of extra pounds will eventually cause fat cells to multiply.)

• About 10 percent of your fat cells die and are replaced each year, whether you’re thin, fat, or somewhere in between.

No one knows why some people end adolescence with more fat cells than others. There’s a good case to be made that it’s hard-coded in your genes (in other words, blame mom and dad). Events during fetal development and childhood might also play a role—for example, chowing down on calorie-rich food early in life could kick off certain processes in your body, preparing it for a life of fat retention. But no matter the reason, it’s clear that some people enter adulthood set up for caloric challenges, with a big family of fat cells. They won’t necessarily gain weight more easily than a naturally lean person, but they’ll probably feel a stronger pull toward that second batch of chocolate chip cookies.

To put it another way: fat people are doing something wrong. But they’re doing it because their bodies are telling them to.

Source of Information : Oreilly - Your Body Missing Manual (08-2009)

The Secret Power of Fat

The connection between fat and hormones is at the forefront of fat research. In the past, scientists assumed that the problems caused by excess fat were the result of its physical burden. They worried that fat would strain bones and joints, plug up arteries, and crush internal organs. But today, many scientists believe that the chemical contribution of fat is more important—and far more dangerous. Although the hormones that fat secretes are critically important in small doses, in large amounts they can trigger runaway inflammation, confuse other organs, and throw off your body’s regulatory processes.

Here’s an example: Osteoarthritis is a painful condition that causes the cartilage in your joints to break down. Studies find that as your body weight creeps up, your risk for osteoarthritis rises along with it. The traditional explanation is that excess weight causes extra wear and tear to important joints like your knees, which is certainly possible. However, increased body weight also increases the likelihood of osteoarthritis in places where weight isn’t all that significant, like your hands. A more recent explanation is that excess fat triggers chemical changes that can wreak havoc on your body (for example, inflammation that attacks the cartilage in your hands).

Source of Information : Oreilly - Your Body Missing Manual (08-2009)

Big Fat Myths

Fat is always on our minds. We waste many productive hours thinking about the fat that’s on our plate, our bodies, other people’s bodies, and (for purely scientific reasons) the bodies of scantily clad celebrities on the Internet. Other body parts don’t come close to getting this much attention, which is probably why fat is the subject of a messy collection of mistakes, myths, and misinformation. Here are some fat factoids you might have encountered:

• Muscle turns to fat. Muscle and fat are different types of tissue, and the body can’t convert one to the other any more than you can transform a pear into a chocolate truffle. However, your fat sits on top of your muscles, which means that a small weight gain can quickly mask those six-pack abs.

• A calorie is a calorie. There are a dizzying range of factors that can influence how well your body transforms food into energy and (ultimately) fat, from the quality of the bacteria in your digestive tract to the combination of nutrients in the food you eat. So-called experts that miss this subtlety warn that a single extra glass of juice a day can add up to dozens of pounds of weight gain over a year, which is clearly nonsense. Other than paranoid dieters, no one eats with such maniacal precision. The truth is that the body is miraculously successful at preserving its preferred weight.

• Thin people have faster metabolisms. This is partly true, in the sense that naturally thin people often expend more energy in small, natural ways (for example, with constant fidgeting). However, people of all body types appear to burn calories in roughly the same proportion to their weight, which means that obese people actually need faster metabolisms to maintain their extra poundage. However, there’s one huge exception: If you start an extreme diet, your metabolism will fight you, slowing itself down to a calorie-conserving crawl. Similarly, pig out in an effort to put on pounds, and your metabolism will speed up to keep you at your current weight.

Source of Information : Oreilly - Your Body Missing Manual (08-2009)

How Fat Controls Your Body

Your body has billions of fat cells. (For example, people with healthy, normal weight carry around some 40 billion fat cells.) Each one is a miniature reservoir for storing fat. Fat cells work in a rather unusual way. When your body squirrels away fat, your fat cells don’t do what you might expect them to—multiply. Instead, they gobble up the extra fat, inflating themselves like rubber balloons. In fact, if you take a close-up look at a fat cell under a microscope, you find that nearly the entire cell is filled with a greasy droplet of fat. The rest of the cell—the cellular machinery that runs the shop—is squeezed to the very edge of the cell, and much more difficult to spot. Early researchers wondered if fat cells actually did any work on their own, or if their squashed functional parts were completely disabled.

Fat cells make up a spongy type of tissue that biologists call adipose tissue. Inside this tissue, your body packs fat cells together in a neat, almost honeycombed pattern. It’s like bubble wrap for your body.

In the past, scientists thought fat cells were simply boring blobs of lard. We now know that they don’t hang around idly—instead, they release massive quantities of hormones that have effects throughout your body. For this reason, many fat scientists (er, make that scientists studying fat) argue that fat isn’t just excess tissue—it’s a smart and powerful organ in its own right.

At this point, it’s natural to ask what these fat-secreted hormones are up to. Although the interaction between fat cells and the rest of your body is fantastically complex, here are some key examples:

• Female fertility. As women know, carrying and delivering a baby is a body-straining odyssey. Without a bare minimum of fat, your body won’t even let you try. If your body decides that you don’t have the necessary fat reserves to live through a pregnancy and nourish a baby, you’ll stop menstruating. Regain the fat, and the deal’s back on.

• Appetite. Fat cells release a hormone called leptin that tells your brain to damp down feelings of hunger. Leptin is often blamed for the nearly inevitable weight gain that follows severe dieting. As you lose fat, your leptin level falls and your brain feels less satisfied, becoming much more likely to trigger a late-night cheesecake craving.

• Regulating the immune system. Fat cells release compounds that fire up parts of your immune system. Too much fat, and these signals get amplified to harmful levels, triggering inflammation deep inside your body. This inflammation can damage your body and lead to other conditions, like heart disease, arthritis, and type 2 diabetes. On the other hand, elite athletes who eat an extremely low-fat diet—say, ultra-marathon runners—end up suppressing their immune systems and becoming more susceptible to infection.

Hormones are special chemicals the body uses to send messages from one place to another. Your fat releases hormones into your blood, where it can travel to other body parts, like your brain.

It might seem that a little extra leptin would make a great diet pill. Unfortunately, it doesn’t work that way. The problem is that your body is far more interested in preventing starvation than in fighting weight gain. If your leptin level rises, your brain adapts to this new level and considers it the “new normal.” Then, when you stop taking the pills and your leptin level falls, hunger quickly sets in. This process, like much of the body’s appetite-control system, is a bit biased. In fact, it looks a lot like a one-way street to more eating.

Source of Information : Oreilly - Your Body Missing Manual (08-2009)

Fat

It can strike fear in the heart of the most level-headed, body-positive person. Wrapping your body just under its outer covering of skin is a gentle, gelatinous blanket of fat. Serving as insulation, cushioning, an energy reserve, and the focus of intense social scrutiny, fat is one body component that the average person spends more effort to remove than to understand. But fat is no lightweight—although it gets a lot of bad press, it’s as essential to your survival as any of your more popular organs.

Fat is also at the heart of a controversial body mystery. Unlike the fine tuned processes in the rest of your body, fat storage is the one mechanism that frequently goes completely off the rails. In the process, excessive fat sets up ordinary people for a dismal collection of health troubles.

It’s hard to overstate just how big the problem is. Compared with other animals, obese humans are biological wonders—pound for pound, the fattest creatures on earth. (If you aren’t already feeling self-conscious, consider this: The percentage of body fat of the fattest humans tops that of even the generously proportioned beluga whale.) Still more remarkable is just how common excessive fat is. Despite billions of dollars, high-powered research, and some seriously good intentions, people are getting fatter year after year, in countries across the globe. In the U.S., more than a third of the population is overweight and another third is obese, leaving less than a third of the population to give everyone else disapproving looks in line at the all-you-can-eat restaurants. Clearly there’s something about the modern world that’s throwing the body’s carefully tuned mechanisms seriously out of whack.

You’ll start to unravel this riddle. You’ll learn why you need fat, how it works, and why your body is so keen to hold on to every ounce of fat it’s got. You’ll also measure your body-fat percentage and learn some techniques that can help you battle excess weight. Along the way, you’ll explore some common questions, like: Do diets really work? Who’s to blame for your bulging belly? And why do some people struggle to count calories while others can down an entire cheesecake and get away scot-free?


The Purpose of Fat
Fat elicits contradictory emotions. Oh, we like it well enough when it coats our fish sticks, but it’s not nearly as appealing when it’s wrapped around our midriffs. And even though fat’s a visceral part of us, we treat it as an unwelcome intruder. Consider how most well-adjusted people can agree with both of these statements:

Every part of the human body is good, proper, and has its own beautiful purpose.

Fat is an evil, evil thing, and I’d do anything to eliminate it.

But before you call the local liposuction clinic, consider this: Fat—a modest amount of it, anyway—is your friend.

The fat in your body cushions your organs and joints, absorbing shocks and protecting them from damage. It also insulates your body against temperature extremes. Less critically, body fat gives you a cushion to sit on and covers hard bone with padding, making hugs much more pleasant. The fat in your diet helps your body absorb certain vitamins, produces compounds that regulate blood clotting and inflammation, and builds structures like cell membranes. Your brain is literally filled with the stuff— by weight, your brain’s more than half fat.

Most important, fat is the body’s energy storage system. In times of plenty, your body stores extra calories as fat, ensuring that none of the effort you spend cooking, chewing, and digesting goes to waste. When food is scarce, your body taps into its fat reserves, burning them to fuel everything your cells do.

This energy storage system kept our distant ancestors alive through tough times and countless famines, while the nibblers and picky eaters perished. The problem is that famines don’t come along as often as they used to. As a result, average people spend most of their lives planted firmly in the first part of the energy-storage equation, hoarding fat for food shortages that never come.

Source of Information : Oreilly - Your Body Missing Manual (08-2009)