The Skinny on Body Fat

Body composition is important not only for physical aesthetic but also for performance and longevity. Here’s what you need to know to swing the percentages in your favor.

FAT.

No group of women fears this word more than those in the fitness industry. Body fat is the target of nearly all workout programming, and all efforts are directed toward burning it, cutting it and losing it. Not that wanting to haul around less body fat is bad — quite the contrary: Obesity is the scourge of both the individual and society at large, and losing a ton of fat would literally do a world of good.

Yet for some, fat loss becomes a slippery slope, and often women push it a little too far when chasing that lean ideal. Because in the end, body fat is still a vital part of our physiology and too little can be just as dangerous as too much.

What the F…

First, let’s get this straight: Bodyweight and body composition are not the same thing. Your bodyweight is simply the number you see on the scale and is really only a measure of how hard gravity is pulling you toward the earth’s center. It measures the total weight of your body — muscle, bones, skin, organs, water weight, hair — even lunch — and what you weigh can fluctuate from day to day depending on what you ate, the time of the month (for women), how much sodium you’re ingesting and stress levels.

Knowing your weight is useful as a gauge of health in some ways, and several studies have shown that people who weigh themselves every day are more likely to stick to a health program than those who don’t because the scale keeps them accountable for their actions. However, it does not take into account the composition of your body — the ratio of fat to lean mass in your person — and is not really a good indicator of health.

Your body composition is the breakdown of what exactly you’re made of: muscles, bones, organs and of course fat. It is often described as the ratio of your fat mass vs. your fat-free mass. However, this is somewhat misleading: A certain percentage of your body fat is actually found within your organs, nervous system and hormones, as well as on the surface of every one of the 37 trillion cells in your body. This “essential fat” accounts for about 8 to 12 percent of total fat for women. The remainder of your fat mass is that bothersome layer we all want to shed — adipose tissue — which lies beneath your skin and is in essence a cache of fatty acids stored in cells as energy reserves and insulation.

Although it may be aesthetically displeasing, some adipose tissue is necessary for normal physiology and plays an important role in the production of sex hormones like estrogen and progesterone. It also facilitates the transport and storage of fat-soluble vitamins and, strangely, plays a role in satiety: The brain takes note of how much fat is stored in adipose cells and can increase hunger signals or reduce your activity level when it feels stores are too low.

Because it’s essentially stored energy, adipose tissue has a very low metabolic cost — in other words, it requires very few calories to maintain. Lean mass is quite the opposite, requiring more calories just to exist, and gaining muscle weight is a good thing for fat loss in the long term because it will cause the body to burn more calories throughout the day. Gaining lean mass will also change your resting metabolic rate (RMR), the calories you burn at rest. Your RMR is highly influenced by body composition, which is why two people of the exact same height and weight can look very different physically and will require very different amounts of food to fuel their physique: The one with more lean mass requires more calories, even if they’re not active that day.

How Low Should You Go?

Women by nature have more essential body fat than men, and a healthy range of total body-fat percentage can swing anywhere from 18 to 30 percent for women. While we all want to see our abs, dropping below the norm can have some negative side effects, ranging from the innocuous — temperature sensitivity and decreased energy — to the more dangerous — loss of muscle mass, depression, reproductive and endocrine dysfunction, heart arrhythmia and kidney damage.

Athletes and fitness pros can often maintain a leaner physique based on their activity level and the amount of muscle they carry. For these women, a year-round 15 to 19 percent body-fat level is not uncommon and can still be healthy. However, the effort required to maintain this level demands more attention to exercise, nutrition, sleep, stress management and mindset. Many athletes who compete in bikini, fitness and figure drop below that number to hit their peak for a competition, but most rebound back to normal once the show is over since it is unhealthy and difficult to maintain such low levels of body fat. This subnorm loss should be done slowly over the course of several months because fluctuating quickly in a larger range — alternating with drastic cuts and rapid gains — can wreak havoc on your endocrine, digestive and immune systems.

For non-stage athletes who want long-term results, slow, steady fat loss is always better because it gives your brain a chance to reset its conservation tactics and learn to accept a lower overall body-fat level. You’ll also want to maintain a body-fat level that allows you to excel at your sport, allowing you to get stronger and keep your hormones and other internal systems in top shape.

Where the F…

Where you store adipose tissue is equally as important as how much you have. Fat stored subcutaneously (beneath the skin) can be deposited anywhere on the body but may be genetically and hormonally influenced to settle in a particular location, like the hips, thighs or belly. And though you might hate your saddlebags, research has found that women who store fat around their butts, hips and thighs have a lower risk of cardiovascular disease and high blood pressure than women who store fat in their abdomens and midsections.

Although genetics primarily control where you store your fat, you do have some control, and actually the type of exercise you do may influence how and where your body will store energy in the future.

For example, fat has been found stored in between muscle fibers in endurance athletes, making for easy energy access during long-distance events. External factors such as hormonal birth control methods also can alter where you store your fat because they trick your body into fake pregnancy every month, causing it to hang on to more fat — particularly around the hips. And bad news for masters athletes: Fat storage increases as you age, and the location shifts more to the midsection since fat storage is highly influenced by reproductive hormones, which wane during menopause.

Why the F…

No two bodies look or function exactly the same, even at similar body-fat levels. Some of us look, feel and function better with slightly higher or lower levels, and the healthy ranges prescribed leave a lot of room for individuality.

Numerous factors dictate your body-fat needs. If you’re trying to get pregnant, for example, you’ll need to carry a little more fat for proper hormone production. And while some athletes still have healthy cycles when relatively lean, others may lose their cycle completely if they drop below 18 to 20 percent. Athletes will also need to carry different amounts of fat depending on what their sport requires for fuel, momentum, comfort and mental focus. Even physique competitors rarely rely on body composition alone to prep for competition. The target “look” that is required for their performance has more to do with overall appearance than reaching an arbitrary number alone.

Unfortunately, when you do trim down, you won’t always lose body fat exactly where you want, nor is that loss evenly distributed across your body. Often, the place you want to lose it the most will be the last to leave, and if you’re wondering at what percent body fat your abs will magically appear — keep wondering: Some people can see visible abdominal definition at higher body-fat levels, while others can get dangerously lean and only see a ghost of a six-pack.

The Other F-Word

Fat composition is just one of many ways we attempt to measure the other, more important F-word — fitness. However, being fit is about way more than being lean: It includes strength, power, speed, agility, endurance, balance, flexibility and much, much more. If you’re an athlete, you’re better off training for the components of your sport that will improve your chances of success, and this often has little to do with how lean or shredded you are. The most important thing is to determine what body-fat level will best support your lifestyle and/or sport. Life is too short, too important and frankly too fun to stress over achieving someone else’s “ideal” number at the expense of your own well-being. Your fat should support your fit.

How the F…

If you want to know your body composition, whether you’re planning to compete or are just curious, there are several methods to consider. But no matter which you choose, none of them is 100 percent accurate (no matter what the salesperson tells you), and the readings can be off as much as 1 to 4 percent in either direction. In other words, if you measure 20 percent body fat in a test, you have just as much chance of being 16 percent as you do of being 24 percent.

Of all the tests, the dual-energy X-ray absorptiometry scan (DEXA) is considered the gold standard, providing you with an X-ray scan of your body showing where you store your body fat. This has a +1 to 2 percent margin of error, which is on the low end of the variability.

No matter which method you choose, you’re better off completely ignoring the resultant percentages since their accuracy is dubious. Instead, use those numbers as a baseline measurement to track change and ensure maintenance over time, making sure your fat mass is going down and/or your lean mass is going up.

When testing, use the same method, test at the same time of day under similar physical conditions, and use the same trainer or technician whenever possible. Also, minimize the room for error with the following steps:

• Avoid alcohol and excess sodium at least 48 hours before the test.
• Don’t consume diuretics (caffeine, tea or soft drinks) for 24 hours before the test.
• Don’t exercise for 12 hours before the test.
• Avoid eating large meals a few hours before the test.
• Maintain normal hydration.
• Empty your bladder at least 30 minutes before as well as right before the test.

Gut Check

Research has shown that carrying excess adipose tissue around your midsection is an indicator of increased risk for disease, but this goes beyond — or rather below — the muffin top. Visceral fat is adipose tissue that is deposited inside the abdomen — not on top of it — and that surrounds and sort of chokes up your internal organs. This kind of fat has been shown to increase the risk for chronic disease more so than the subcutaneous version because it is hormonally active, decreasing your body’s ability to regulate blood sugar and increasing the risk of high blood pressure or cardiovascular disease. It also produces inflammatory substances and disrupts the hormones that regulate appetite, mood, weight and brain function.

Prevent the deposit of visceral fat by avoiding refined carbs and processed foods, which cause a spike in blood sugar, as well as high-fat and high-calorie foods, which inevitably get stored as fat. Research has also shown that eating trans fats may be associated with increases in visceral fat, and a study in The Journal of Clinical Investigation also uncovered an association with high-fructose corn syrup and the deposit of visceral fat. But make sure you replace your regular soda with water, tea or coffee rather than diet soda: A study in the Journal of the American Geriatrics Society found that artificially sweetened soda was associated with an increase in waist circumference, which is an indicator of increased visceral fat.

Fun Fat Fact 

Fat tissue comes in a range of colors — white, brown and beige. White fat cells are those that are most obvious and that contain the highest concentration of fat globules. Brown and beige fat cells, however, are smaller, hold fewer fat globules and contain mitochondria, giving them their brown color. This kind of fat actually burns calories to generate heat, and research has shown that as little as 2 ounces of brown fat can burn several hundred calories per day! It has also been shown to positively affect insulin sensitivity and metabolism, reducing your risk of diabetes and heart disease. Exercise – specifically aerobic exercise — can actually lead to the “browning” of white fat cells, turning dormant, inactive tissue into more metabolically expensive tissue that burns rather than stores calories.