Metabolic Myths

Age-defying ways to rev the engine

Over a cup of tea recently, a 40-something friend confided that she’d had a glimpse of the future and she didn’t like it. She had decided to weigh herself that morning, something she hadn’t done in a while. When she stepped on the scale, the needle climbed to a point where it hadn’t gone since her pregnancy nine years before. “What’s happening to me?” she lamented. “My metabolism must be starting its middle-age slowdown.”

Metabolism, a greatly misunderstood process of the human body, takes the brunt of many a middle-age whine. People conclude that a slower metabolism is an inevitable part of aging and beyond their control. The truth, however, is more reassuring. Our bodies do change as we age, and metabolism can take a dive as a result, but we hold the key to avert this decline.

Metabolism, the process by which our bodies burn calories (food energy), has three components: resting metabolic rate, the thermic effect of food, and physical activity. Resting metabolic rate (RMR) is the energy we use at rest to perform basic body functions like breathing and sleeping. In most people, this accounts for about 60 to 70 percent of their total daily energy expenditure (about 1,450 calories a day for a 140-pound woman). Because muscle is the body’s metabolically active tissue, RMR is almost totally determined by the amount of lean body (muscle) mass a person has. For the most part, we all have the same metabolism per amount of lean body mass. Most women have more body fat in proportion to muscle mass than men, and thus women generally have metabolic rates that are 5 to 10 percent lower than men of the same height and weight. Unfair as it may be, that means most men use up more calories just sitting on the couch than the women sitting next to them do.

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The RMR of most people goes down by 2 to 3 percent with each decade once we reach our thirties, a direct result of the loss of muscle mass that often accompanies aging. Luckily, we can prevent this loss with regular strength-training exercises, which are designed to build or preserve muscle.

The thermic effect of food (TEF) is the energy we use to burn calories or, more explicitly, to digest, absorb and metabolize our food. When you eat a 110-calorie snack, for example, 10 of those calories are used for TEF. It is a relatively small portion of our total metabolism: about 10 percent, or 240 daily calories, for a 140-pound woman.

Our greatest control over metabolism lies with physical activity. It’s also the most easily thwarted, living as we do in a world of drive-through banks, escalators, leaf blowers and the omnipresent computer. Unless you are one of the rare people whose job requires you to be moving throughout the day, you probably need to work deliberately at increasing your physical-activity level. The less time you have for exercise, the more vigorously you should move. I can jog 21⁄2 miles in 30 minutes or I can burn the same number of calories on a leisurely hourlong walk. I frequently wear a step-counter to monitor my goal of 10,000 steps a day, the equivalent of 5 miles. After untold hours in front of my computer, if I don’t spend at least 45 minutes running or in an exercise class, I don’t come anywhere close to my goal. If I exercise enough I can indulge my love of good food and savor a scrumptious dessert or great glass of wine several times a week without adding pounds.

Even fidgeting, which comes naturally to some people, can increase energy expenditure above resting levels by 300 to 600 calories per day. My oldest son is one of those people who seem to be blessed with “thin” genes. But after being around him for more than two decades I think I have a good idea what’s going on: he’s a fidgeter. He is constantly tapping his foot and shifting in his seat. (When he was little it seemed we were always pleading with him to sit still at the dinner table.) Compared to sitting still, browsing in a store takes twice the energy, while a slow walk (2 to 3 mph) can triple energy expenditure.

I have no doubt my friend will get her weight back to where she’d like it. She may have to invest in some free weights and a little more time running, but that’s all under her control. We certainly can’t stop the years ticking by, but keeping our metabolism youthful and burning calories at a healthful rate is well within our grasp.

Calories Burned in Action (over 1 hour)
(not counting the 77 calories burned at rest)

Chewing Gum: 11
Fidgeting: 70
Walking 1 mph: 119
Walking 2 mph: 158
Walking 3 mph: 228

Recipes

Peppered Salmon Steaks with Yogurt-Lime Marinade
The yogurt marinade, with hints of lime and ginger, makes the salmon wonderfully succulent.

Makes 4 servings

ACTIVE TIME: 20 minutes
TOTAL TIME: 50 minutes
EASE OF PREPARATION: Easy

1/2 cup low-fat plain yogurt
1 tablespoon canola oil
1 tablespoon lime juice
1 teaspoon honey
1 tablespoon minced fresh ginger
1 clove garlic, minced
1/4 teaspoon salt
1/2 teaspoon freshly ground pepper
4 1-inch thick salmon steaks
Lime wedges

1. Whisk together yogurt, oil, lime juice, honey, ginger, garlic, salt and pepper in a shallow nonreactive dish,. Add fish steaks and turn to coat with marinade. Cover and marinate in the refrigerator for at least 30 minutes or up to 1 hour, turning once.
2. Preheat grill.
3. Coarsely grind pepper onto steaks and gently press in. Oil the grill (see Tip). Grill the steaks, turning once, until the fish is opaque, about 10 minutes. Serve immediately with lime wedges.

NUTRITION INFORMATION: Per serving: 268 calories; 16 g fat (3 g sat, 7 g mono); 69 mg cholesterol; 5 g carbohydrate; 24 g protein; 0 g fiber; 234 mg sodium; 503 mg potassium. Nutrition bonus: Selenium (61% daily value). 0 Carbohydrate Servings.

TIP: To oil the grill rack: Oil a folded paper towel, hold it with tongs and rub it over the rack. (Do not use cooking spray on a hot grill.) When grilling delicate foods like tofu and fish, it is helpful to spray the food with cooking spray.

More Healthy Salmon Recipes and Cooking Tips

Sauteed Watercress
Peppery watercress is nicely balanced by sweet garlic and tart vinegar in this quick saute.

Makes 2 servings, about 1/2 cup each

ACTIVE TIME: 10 minutes
TOTAL TIME: 10 minutes
EASE OF PREPARATION: Easy

1 clove garlic, minced
2 teaspoons extra-virgin olive oil
2 4-ounce bags watercress, tough stems removed
Champagne vinegar or white-wine vinegar to taste
Salt & freshly ground pepper to taste

Saute garlic in oil in a large nonstick skillet until fragrant. Add watercress. Cook, stirring often, until wilted. Stir in vinegar, salt and pepper to taste.

NUTRITION INFORMATION: Per serving: 56 calories; 5 g fat (1 g sat, 4 g mono); 0 mg cholesterol; 2 g carbohydrate; 3 g protein; 1 g fiber; 116 mg sodium; 350 mg potassium.
0 Carbohydrate Servings.

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Old-Fashioned Apple-Nut Crisp
Apples and nuts are a classic—and healthful—combination, especially when you cut back on the saturated fat that typically tops this sweet treat. Our version is just as delicious, and allows the flavor of the hazelnuts to shine through. A dollop of Vanilla Cream or scoop of vanilla frozen yogurt finishes this homey dessert beautifully.

Makes 8 servings

ACTIVE TIME: 50 minutes
TOTAL TIME: 1 1/2 hours (including cooling time)
EASE OF PREPARATION: Easy

5 medium-large crisp, tart apples, such as McIntosh, Empire, Granny Smith or Cortland, peeled and thinly sliced (about 6 cups)
3 tablespoons granulated sugar or Splenda Granular
1 tablespoon lemon juice
1 teaspoon ground cinnamon, divided
2/3 cup whole-wheat flour
1/2 cup old-fashioned rolled oats (not instant)
1/2 cup packed light brown sugar
2 tablespoons butter, cut into small pieces
2 tablespoons canola oil
2 tablespoons frozen apple juice concentrate, thawed
1/3 cup coarsely chopped hazelnuts or walnuts

1. Preheat oven to 375°F. Coat an 8-inch square (or 2-quart) deep baking dish with cooking spray.
2. Combine apples with granulated sugar (or Splenda), lemon juice and 1/2 teaspoon cinnamon in a large bowl. Toss to mix. Transfer to the prepared baking dish, cover with foil and bake for 30 minutes.
3. Meanwhile, combine whole-wheat flour, oats, brown sugar and the remaining 1/2 teaspoon cinnamon in a medium bowl. Mix to blend. Using your fingers (or a fork or pastry blender), cut in butter until evenly distributed and there are no chunks. Stir in oil, apple juice concentrate and nuts; toss well until evenly moistened and clumpy.
4. Remove the foil from the baking dish and scatter the topping evenly over the apples. Bake uncovered until the topping has browned and the fruit is soft and bubbling, about 30 minutes more. Let cool for at least 15 minutes before serving.

NUTRITION INFORMATION: Per serving: 274 calories; 10 g fat (3 g sat, 4 g mono); 8 mg cholesterol; 45 g carbohydrate; 3 g protein; 6 g fiber;1 mg sodium; 231 mg potassium. Nutrition bonus: Manganese (17% daily value). Exchanges: 2 1/2 other carbohydrate, 2 fat (saturated). 2 1/2 Carbohydrate Servings.

Per serving with Splenda: 2 1/2 Carbohydrate Servings; 265 calories; 43 g carbohydrate.

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From www.eatingwell.com with permission.  © 2008 Eating Well Inc.