10 mitos sobre la grasa corporal

¿Cuál es una de las cosas sobre la grasa corporal que la mayoría de la gente cree que es verdad? ¿Qué tal este? El músculo quema más calorías que la grasa. Si bien sí, nuestro músculo esquelético quema más calorías todos los días que nuestra grasa corporal, no es tan notable como podría pensar. Es realmente una diferencia sorprendentemente insignificante cuando hablas de cuántas calorías se consumen para obtener energía mientras estás sentado. Las calorías que el cuerpo necesita solo para cuidar su supervivencia se denominan gasto de energía en reposo, y cuando no está haciendo ejercicio o gastando su energía, su tejido adiposo quema dos calorías por cada libra de su peso corporal total, pero su músculo esquelético quema solo seis calorías por libra [fuente: McClave ].

Lo que más energía consume todos los días es el cerebro. Engulle alrededor del 20 por ciento de las calorías que quemas, lo cual es sorprendente si consideras que el cerebro representa solo alrededor del 2 por ciento del peso total de tu cuerpo [fuente: Ray ]. Y a pesar de que representan solo el 5 por ciento del del peso del cuerpo, el corazón, el hígado y los pulmones combinados consumen la mayor cantidad de energía, alrededor del 50 por ciento [fuentes: McClave , Ray ]. Entonces, aunque el tejido muscular quema más calorías que grasa, sigue siendo un porcentaje relativamente pequeño del consumo total de calorías del cuerpo.

¿Cuáles son otras creencias comunes sobre la grasa corporal? ¿Ese músculo pesa más que la grasa? ¿Que, inevitablemente, la propagación de la mediana edad nos alcanzará a todos? Como la mayoría de los estadounidenses, el 69 %, tiene sobrepeso y más del 35 % se considera obeso, tal vez sea hora de desmentir algunos mitos sobre la grasa corporal, desde su relación con nuestras hormonas hasta la mejor manera de perderla.

1. Toda la grasa es igual
2. La celulitis es causada por impurezas y toxinas
3. Restringir las calorías para bajar de peso es bueno; Restringirlos drásticamente es aún mejor
4. Su grasa corporal no puede ser demasiado baja
5. Cardio es la única forma de perder grasa
6. La reducción de manchas puede suceder
7. A medida que envejece, el aumento de grasa es inevitable
8. Las células grasas solo almacenan grasa
9. Convierta la grasa en músculo, el músculo en grasa
10. Comer grasa engorda

Durante mucho tiempo se ha pensado que los adultos tienen un solo tipo de grasa: la grasa grumosa blanca/amarilla a la que se culpa por las llantas de repuesto. La grasa blanca almacena cualquier caloría extra que ingieres para tus futuras necesidades energéticas, pero si tienes demasiada, también se asocia con problemas de salud como resistencia a la insulina y enfermedades del corazón . Sin embargo, resulta que no es el único tipo de grasa en nuestro cuerpo.

Los seres humanos también tienen grasa parda, ubicada en depósitos en el cuello y alrededor de la clavícula. Aunque las personas tienen una gran cantidad cuando son niños, tenemos mucho menos cuando somos adultos, y algunos de nosotros no tenemos nada en absoluto: los estudios han encontrado que las personas delgadas tienen más probabilidades de tener grasa marrón que las personas con sobrepeso. u obeso, pero nadie está seguro de por qué, al menos no sin más investigación [fuente: Doheny ].

La grasa marrón no se comporta de la misma manera que la grasa blanca. La grasa parda obtiene su color y nombre de sus mitocondrias ricas en hierro, y los científicos describen su función como más similar a la del músculoque como siempre hemos pensado que se comportaba la grasa. Por ejemplo, la grasa parda es un buen aislante porque quema la grasa blanca para obtener energía. ¿Quemaduras? Si. Mientras que la grasa blanca almacena energía y está asociada con el aumento de peso, la grasa parda es termogénica. Quema energía para el calor y puede desempeñar un papel en la pérdida de peso. En las circunstancias adecuadas, una persona saludable promedio con un peso saludable podría quemar hasta 250 calorías en un solo día debido a sus reservas de grasa parda, y resulta que todo lo que se necesita es un ambiente frío para activar la grasa parda. Cuanto más grandes sean nuestras reservas de grasa parda, mayor será el beneficio; solo 2 onzas (56 gramos) de actividad de grasa parda podrían quemar hasta 8 a 9 libras por año [fuentes: Cypress , Raloff ].

La celulitis es esa piel con hoyuelos que se desarrolla generalmente alrededor de nuestros muslos y glúteos, y tal vez en nuestras caderas y rodillas, y aunque muchos de nosotros podemos pensar que es antiestético, es inofensivo. No es causado por toxinas o impurezas y, a pesar de todas las afirmaciones sobre soluciones que van desde el drenaje linfático hasta los tratamientos con crema de cafeína, no existe una cura porque en realidad no es más que grasa.

Todos tenemos el potencial de desarrollar celulitis: sobrepeso, delgados, jóvenes, viejos, hombres, mujeres, aunque afecta principalmente a las mujeres. Hasta el 90 por ciento de las mujeres (y solo el 10 por ciento de los hombres) desarrollan celulitis, que se cree que es causada, al menos en parte, por la predisposición genética y la disminución de los niveles de estrógeno . La dieta y un estilo de vida sedentario también juegan un factor en si una persona desarrollará celulitis, al igual que la estructura del tejido conectivo debajo de la superficie de la piel [fuente: Harmon ]. Este tejido conectivo es un marco de fibras de colágeno que conecta la piel y el músculo. La celulitis aparece cuando los depósitos de grasa que se acumulan debajo de la piel sobresalen a través de ese marco.

Drastically cutting the number of calories you eat may sound like a fast way to lose a few pounds , and it can be, but in the long run, it's bad news. In fact, there's a high likelihood that crash dieters who restrict the number of calories they consume to 800 or fewer per day will, in addition to being hungry, regain the weight they've lost within the first six months after giving up the diet.

Eating too few calories, less than 1,200 per day, doesn't just cause fat loss; it also causes muscle loss. And in the long term, severe calorie restriction can cause anemia, dizziness, headaches , low blood sugar, liver and kidney problems, and a host of other complications. It also triggers the body to conserve its potential energy (that means it hoards calories and uses them slowly). Crash dieters often find that their body fat percentage ratio is worse after dieting than before they started cutting calories [sources: Hensrud, Zelman].

Your body fat conserves your energy, keeps you warm, cushions your organs and allows the body to maintain the basic functions that keep you alive. Your ideal body fat percentage will be different from that of other people. How much each person has depends on some things that can't be changed including age, bone structure, biological sex and genes, in addition to things we can change, such as whether we lead an active or sedentary lifestyle.

Too much body fat is associated with chronic disease such as type 2 diabetes , cardiovascular disease and some cancers. But the pendulum can swing too far in the other direction. You can have too little body fat, which poses a different set of health issues.

A body needs to have a certain percentage of fat in order for it to be able to function: Women need about 13 percent body fat and men about 3 percent. This is your essential body fat and doesn't include any fat stores. In addition to essential body fat, a body also needs storage fat. On average, 15 percent of a woman's body weight should reflect her storage fat, and that number is about 12 percent for men.

When body fat drops lower than 14 percent for women and 8 percent for men, health risks increase, including everything from reproductive dysfunction (such as amenorrhea in women), dehydration, starvation, loss of muscle tissue and premature osteoporosis , in addition to complications such as organ and nerve damage [source: UPDR].

Doing cardiovascular (aerobic) exercise such as walking, biking or — everyone's favorite — the Stairmaster is good for you. It reduces heart disease risk by keeping the heart and lungs in shape, helps meet weight loss goals and keeps your whole body healthier.

But if your focus is to burn the most fat, it's not actually the best choice.

You may think of weight training (also called strength or resistance training) as the way to build muscle mass, which it is, but weight-bearing exercises have also been found to be better at burning abdominal fat than cardio exercise alone. Two 15- to 20-minute resistance training sessions every week have positive effects on everything from your resting metabolic rate to your blood pressure and how well your body handles insulin — and it's been found to be better at keeping the waistline from expanding than cardio alone. Combine the two for the best results [sources: ACSM, Winett].

Unlike building muscle by targeting different muscle groups, such as abs or glutes, when you lose fat you lose it systemically — that means you lose it all over, not just in one place. Crunches may tighten the abdominal muscles, but those crunches won't specifically reduce your abdominal fat. The reason? Incompatible fuel. Fat cells store triglycerides. But when your body calls upon its energy reserves to be used as fuel, those triglycerides need to be converted into a fuel that your muscles are able to use — glycerol and fatty acids — and those can enter the bloodstream from anywhere fat is stored in the body, mid-section or otherwise [source: Perry].

Age-related weight gain is typically centered around our mid-section; it's abdominal fat (called visceral fat), and it begins to settle in around the time you turn 40 [source: Melone]. It's true that as people age, metabolism slows down and the amount of fat in the body increases, but gaining weight because of those changes isn't inevitable. You do need to kick things up a notch to stave it off, though. The trick? Weights .

Aside from a sensible diet, adding weight training to a cardio-centric exercise routine will help combat age-related loss of muscle mass, called sarcopenia. Combining weight training with cardiovascular exercise also increases bone density, balance and flexibility. And weight training has been found to be better at burning stubborn abdominal fat than aerobic exercise, especially as you age. Plus, the more muscle mass you maintain as the years go by, the lower your chances of dying prematurely [source: Srikanthan].

Body fat has two primary functions. It will come as little surprise that our fat cells store lipids for future energy needs, but did you know that body fat, which is adipose tissue, is considered an endocrine organ? Fat cells are biologically active, and they produce hormones such as leptin, which influences our appetite, and adiponectin, which controls how well the body regulates glucose and breaks down fats.

There's a bit of a chicken-and-egg scenario when it comes to our body fat, though, as we know that an excess or lack of certain hormones can cause us to gain or lose weight, but our weight also directly affects the amounts of these hormones in the body. If the wrong messages are sent throughout the body, there's a risk of insulin resistance, elevated levels of lipids in our blood (hyperlipidemia) and vascular inflammation.

You've probably heard that if you don't exercise or work out, your muscle will turn to fat. If that was a concern, stop worrying about it; it's not possible. Nor can fat turn into muscle. Fat and muscle are different types of body tissues — fat is adipose tissue, and muscle is protein — and you can't change one type of tissue into another. While it may appear that you're turning fat into muscle or muscle into fat when you get slack or get serious about exercise, that appearance is only because fat is less dense than muscle, which means an ounce of fat takes up more space inside the body than an ounce of muscle does.

So if fat doesn't turn into muscle, where does it go when you lose weight? Does it just shrink? Does it melt into energy that you burn off? Researchers studying this biochemical process tracked fat molecules to figure out exactly where fat goes when you lose it, and they use a chemical formula to calculate the process: C55H104O6 + 78O2 → 55CO2 + 52H2O + energy. As it turns out, mostly, we just exhale it. If you were to lose 22 pounds (10 kilograms) of body fat, 20 pounds (9.4 kilograms) would be released as carbon dioxide (CO2) when you breathe; the remainder would become water that is excreted in our urine, sweat or tears [source: Meerman].

While it's true that some fats are worse for us than others — we're looking at you, LDL cholesterol -raising, man-made trans fats — it's not true that eating dietary fat makes us fat. Calories are what make us fat. You gain weight when you eat more calories than you burn, whether those calories come from fat, carbohydrates or protein.

Regardless of whether a fat is saturated or unsaturated, healthy or unhealthy, all dietary fats contain about the same amount of calories. Fats give you the most energy when you eat them because they're more calorically dense than protein and carbohydrates, ounce per ounce. While there are about 112 calories in one ounce of protein or carbohydrates, one ounce of fat contains about 252 calories [source: Youdim].

Author's Note: 10 Myths About Body Fat

I didn't end up using this in my final draft, but it's cool, so I'm going to share it here. Did you know that the average adult brain consumes about 12 watts each day, just one-fifth of the power a standard 60-watt bulb needs? That's right: 12 watts. That's the same wattage your iPad power adapter uses.

Let's look at how that math works out. We're going to assume that your body's resting metabolic rate — that's the energy your body needs to take care of just the vitals while you lounge about — is 1,300 kilocalories. That's just about 15 small calories (also called gram calories) every second in a 24 hour day. But we can't convert small calories straight to watts, so let's first turn them into joules: 1 small calorie is roughly 4 joules, which then means that 15 small calories per second equals 60 joules per second. And 60 joules per second is the equivalent of 60 watts. Knowing that the brain consumes 20 percent of our total resting energy, 20 percent of 60 watts equals 12 watts.

Phew.

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