article

08.25.09

5 Metabolism Myths Debunked

Find out how metabolism affects the way your jeans fit, how your genes may or may not affect your metabolism—and whether eating hot peppers will help you lose weight.

Everyone knows someone with a crazy fast metabolism: the girl who eats junk food and doesn’t gain a pound, or the guy who drinks as many beers as he wants without growing a beer belly.

Are these people superhuman, endowed with metabolisms faster than a speeding bullet and more powerful than a bacon cheeseburger? Did they get lucky in the genetic lottery? Or are they secretly going to the gym when no one’s looking?

It’s probably a combination of all three, though “superhuman” may be stretching it. Metabolism, that mysterious process of energy production, is often the reason—and the excuse—many people rely on for understanding why bodies are big or small, fat or lean. But what is metabolism, really?

Increased muscles and muscle density will lead to the body burning more calories, which in turn will raise the body’s basal metabolic rate.

Metabolism is commonly understood to be the rate at which the body burns calories. This is only half true. Metabolism is the process by which the body breaks down food and converts that food to energy. Those two steps—the breaking down and the rebuilding—are processes called anabolism, or constructive metabolism, and catabolism, or destructive metabolism. In anabolism, small molecules are changed into larger, more complex molecules of carbohydrates, proteins, and fats (the holy trinity of nutrition). Anabolism requires the input of energy, in the form of food calories, and is the process by which the body stores energy. In catabolism, cells break down those large molecules to release energy and dispose of waste. This energy release provides fuel for anabolism. In this way, anabolism and catabolism exist in balance with each other and are the ying and the yang of metabolism.

So what about burning calories? Seriously, how does she eat French fries and stay so thin? It depends a lot on what else she’s eating, and how much exercise she gets. The golden rule of metabolism is that if energy consumption (calories) and energy production are equal, overall weight will stay the same. Weight loss occurs when the amount of energy the body expends is greater than the amount of energy the body consumes. If the body consumes more calories than it burns, those calories are converted into energy and stored as fat. Seems pretty simple. And it is, so long as fad diet mumbo-jumbo and metabolism-boosting supplements aren’t in the way.

Here are five metabolism myths, debunked with help from Marc Plano, functional diagnostic nutritionist, holistic health counselor, and founder of The Plano Program:

Myth 1: Metabolism is genetic and can’t be changed. False. Well, partly false. All humans (and actually all living things) are born with the ability to break down food in order to create energy. In this sense, metabolism is genetic. “Metabolism is as unique as a fingerprint, some people metabolize food very fast and others very slow,” says Plano. Whether metabolism is “fast” or “slow” is determined by metabolic rate, called basal metabolic rate or BMR, which is the amount of calories one burns while at rest. Even at rest the body is active—organs are working, cells are growing and dying, digestion is occurring—and energy is being used for these processes. Someone with a low BMR will burn fewer calories while at rest, while someone with a high BMR will burn more calories while at rest.

What’s burning the calories while the body is resting? Muscle and fat, though not equally. For every pound of muscle the body burns 35 calories a day, while for every pound of fat burns just two calories per day. Increased muscles and muscle density will lead to the body burning more calories, which in turn will raise the body’s BMR. So weight training is a surefire way to raise BMR. But aerobic activity, too, will help the body to burn calories, not only from the immediate activity but also from the calories that will be used later, while the body is resting. All this work will ultimately increase BMR. So even if slow metabolism is in your genes, you don’t have to live with it.

Myth 2: Metabolism is the same for men or women, no matter their ages. This one is double untrue. Across the board men have higher BMR simply because they’re men. Men have more lean muscle than women and also have larger organs than women, which means that while at rest men are burning more calories than women are. “Muscle mass is your body’s fat burning furnace,” says Plano. “The more muscle mass you have, the more calories you burn at rest.” On average, men have nearly 10 percent higher BMR than women. And women have a layer of subcutaneous fat, which pretty much never goes away no matter how many crunches a girl does, and fat is always going to burn fewer calories than muscle. “Men typically have a faster metabolism, but certainly don’t have more discipline,” Plano adds.

Additionally, as people age metabolism slows down. This isn’t a function of age per se, but of muscle deterioration and the biological inclination toward weight gain. Here’s another happy fact for men: Men maintain muscle density longer than women, and so as a woman’s BMR declines (starting in her 40s) a man’s metabolism won’t slow until he’s at least a decade older.

Myth 3: Hot peppers and green tea will speed up your metabolism. Unfortunately, false. There are no foods that will speed up metabolism. The good news is you can stop putting hot sauce on absolutely everything. While some studies have shown that very spicy foods can increase metabolism, the boost won’t last and after about 30 minutes the rate of metabolism will be back where it started. The same is true of green tea, which is noted for its wealth of antioxidants: Any spike in metabolic rate will be merely a spike and not a permanent change. And even if that spike is appealing, the metabolic process wouldn’t speed up in such a way as to influence weight loss. Since weight loss is the result of more energy being spent than consumed, a spike in metabolic rate will help the body burn calories more quickly but will not affect overall metabolism in a noticeable way. The New York Times reports that while hot peppers offer a “bump in heat generation, which helps burn more calories immediately after a meal…spicy foods can increase metabolism, though only to a minor extent.”

So what can you eat to burn calories and jump-start your metabolism? The short answer is “a balanced diet,” which means foods that are high in protein and low in carbohydrates and fat. Here’s the basic science behind carbs: The body easily converts simple carbohydrates (such as fruit, sweets, and soda) and sugar into glucose, which is absorbed into the bloodstream. As the amount of glucose in the body increases, the pancreas responds by producing insulin, a hormone that moves the sugar from the blood into cells where it can be stored as energy. The non-scientific term for this process: sugar rush. The unintended consequence: weight gain. “Insulin is your body’s fat storing hormone,” says Plano, “and high insulin yields body fat storage. Simple carbs elevate insulin, increase hunger, promote fat storing, and increase the risk of many disease states and inflammatory conditions such as cardiovascular disease and type II diabetes.” The same is not true of complex carbs, however, which take more energy for the body to convert into glucose. Complex carbs such as whole grain bread, whole grain pasta, and starchy vegetables are slower to convert to glucose than simple carbs because they haven’t been refined, or already broken down, as white sugars have. The more time the body takes to convert carbs to glucose, the longer the body will feel full, and the harder metabolism will be working to break down the carbs. “High-fiber, slow-burning carbs keep insulin in balance, which keeps your body out of a fat-storing mode, regulates energy, and provides a sense of satiety,” Plano says.

The ultimate pro-metabolism food is protein: poultry, fish, eggs, nuts, seeds, and legumes such as beans and lentils. Metabolism breaks down proteins into amino acids, which the body uses to maintain muscles, blood, and body organs (all things that help keep BMR high). Plano notes that “protein is vital for survival. Protein is a part of every cell in your body, and no other nutrient plays as many different roles in keeping you alive and healthy.” Protein is also much more difficult for the body to break down than simple or even complex carbs, and requires about 25 percent more energy for digestion. This means that in the process of breaking down protein-packed foods, the body is expending lots of energy, which ultimately helps increase metabolism in the long run.

Myth 4: Eating one big meal per day will boost metabolism. “There are many studies being done in this area right now,” says Plano. “In my opinion, eating small, frequent, multiple meals with the concentration on whole foods with minimal processing are best.” Why? Because skipping meals or not eating will ultimately slow down metabolic rate. Without sufficient nutrients, cells will readjust and begin to function on smaller amounts of energy, which they can do only by storing more fat in anticipation of these periods of nutrient deprivation. “Eating frequently keeps your blood sugar stable reducing cravings, keeps metabolic rate high, and consistently nourishes the body with crucial vitamins and minerals.” By eating small, low-calorie, high-protein meals throughout the day (five or six are the recommended number of meals by nutritionists), the body’s energy supply will be constant and calories will be steadily converted into energy, which means metabolism will be working hard and BMR will be speeding up.

Myth 5: Everything eaten after 7 p.m. turns to fat. The premise behind this myth is that since you’re presumably sleeping a few hours after 7, you can’t be burning calories. And if you’re not burning calories, you must be gaining weight. Not true. “Eating after a certain time does not automatically mean that you are going to store that food as fat,” says Plano. Though metabolism slows down while the body is sleeping, metabolism never stops working entirely. One of the reasons that this rule was made so popular is that it’s an easy way to control late-night binging and unhealthy nighttime snacking. If you’re hungry after 7 or 8 or even 9, you should eat, but eat healthfully: “Eating high-sugar foods or carb-dense foods before bed is a great way to pack on some unwanted pounds,” Plano says. If you’re looking to set up rules around when you should and shouldn’t eat, try this one: eat breakfast in the morning. When you wake up in the morning, your body hasn’t ingested a single thing in six to nine hours, and as a result metabolism has slowed by about 15 percent. Your metabolism won’t speed up until the body can produce energy, which comes from the ingestion of calories. Remember: metabolism is all about the give and take, the ying and yang, of energy consumption and energy production. Balance is key.

Here are some recipes for dishes that may not boost your metabolism on their own, but combined with exercise and regulated portion size will get you on the right track to increased BMR.

Grilled Salmon with Fresh Blueberry Corn Salsa

by Martha and Linda Greenlaw

Blueberries are high in antioxidants, and salmon is a good source of Omega 3 fatty acids, which aid in the metabolism of protein.

Grilled Lemony Chicken with Asparagus

by Leslie Revsin

Chicken breasts are high in protein and low in fat, and asparagus is low in calories and contains no fat.

Spicy Chipotle Turkey Burgers

by Sally Sampson

Lean turkey meat finds new life in the deep, smoky flavors of chipotle in adobo.

Red Beans and Red Rice

by Judith Finlayson

Red beans and rice are a complete protein, and very filling, too.

Plus: Check out Hungry Beast, for more news on the latest restaurants, hot chefs, and tasty recipes.

Sarah Whitman-Salkin is an editor at Cookstr.com. She lives in New York City.