Changing Your Fat-Burning Chemistry

Metabolic myths and realities

Basal metabolic rate (BMR) is measured at rest, reclining, 12 to 18 hours after a meal, and reflects the amount of energy the body uses for basic functions such as breathing, thinking, central nervous system activity and pumping blood and oxygen throughout the body. Metabolic rate is the speed at which the body burns calories at any given time, or how quickly energy is expended. It is measured in calories per minute (or kilocalories in scientific jargon), and accounts for up to 75 percent of the total number of calories burned during the day. An individual could potentially burn 60 to 75 calories per hour, or about 1,440 to 1,800 calories per day, just by sitting.

The speed of basal metabolic energy depends primarily on body composition. Research shows that the more lean muscle mass, the faster the metabolism. Another factor affecting energy expenditure is something called "dietary induced thermogenesis" (digesting, transporting and storing food). This is the least significant in terms of calories, and accounts for about 10 percent of total calories expended (about 75 to 200 calories burned per day). The third factor is activity, which accounts for approximately 15 to 35 percent of total calorie burning. Any activity we engage in, whether it's running, walking or fidgeting burns calories above and beyond our BMR.

Some people have a higher metabolism than others, which can vary as much as 30 percent. We all know people who can eat plates of fettuccini, polish off a quart of ice cream, go back for seconds and still not gain weight. Others swear they eat "like a bird" and just looking at food makes it go straight to their hips.

Factors fanning the fat flame

The main factors influencing BMR include age, gender, genetics, hormones, diet and activity level. Of the list, there are only two that we can actually control.

Age. Starting near age 30, many people begin experiencing a decrease in metabolic rate. Researchers state, however, that this decrease is more likely a result of loss of lean muscle mass and inactivity than the aging process itself. Some studies state that a sedentary lifestyle explains as much as 70 percent of the difference in weight gain between older and younger people.

Genetics. Some say genetics play a small part in determining metabolic rate. Judith Stern, professor of nutrition and internal medicine at the University of California at Davis, and vice president of the American Obesity Association, states, "Genetics is important. But you can't exactly choose your parents."

Hormones. Thyroid hormones regulate metabolic rate. A disorder of the thyroid gland could affect metabolic rate, however only a small percentage of the population are affected by this.

Gender. Men have it better than women here. Generally, men have more lean or "fat-free" tissue than women, thus, they typically have a faster metabolism. Women, on the other hand, are built for fat storage, particularly during puberty, pregnancy and menopause. They have what it takes to store fat quickly and efficiently.

Key players: Diet and exercise

It's true; the literature recommends no more dieting. Crash diets are out, anti-diets are in. More emphasis is being placed on the percentage of muscle and fat, and less on total body weight. Dieting shuts off metabolism and causes a loss of lean muscle mass. For every diet, there is an equal and opposite binge. Statistics show that people gain back more weight after dieting, and with a higher percentage of body fat. These are abysmal statistics. William J. Evans, director of the Geriatric Nutrition, Metabolism and Exercise Program at the University of Arkansas for Medical Sciences, Little Rock, Ark., states, "By cutting back in calories, you will see an immediate drop in metabolic rate."

In theory, the number of calories you take in should equal the number of calories you burn. This may sound simple, but most of us struggle to achieve this balance. Cutting calories is not the answer. Restricting calories robs the body of necessary nutrients, which slows metabolism in an effort to conserve energy. This sets the stage for fat storage. The human body has a sort of built-in survival mechanism that fights dieting. Weight loss is primarily muscle lost, not body fat (especially the more restrictive the dieting). Some studies show that this "famine-fat" acceleration cycle makes for more fat gain with each consecutive period of dieting.

Michael Buono of the Department of Exercise and Nutrition Science at San Diego State University, states, "Weight loss should be no more than one to two pounds per week. Losing more weight than that, although physiologically possible, usually leads to losses in fat-free (i.e., muscle) mass, which is usually not desirable."

What about the composition of the diet? Most researchers agree that a diet high in complex carbohydrates and low in fat (all types) is the best bet. Evans remarks, "It's quite possible to manipulate metabolic rate. Newer evidence shows a diet high in complex carbohydrates has a 'thermogenic' quality which helps to burn more calories. BMR goes down when you undereat." Stern states, "Changing from a low- to a high-fat diet raises set point for many people. The evidence is cleanest in laboratory animals....Unless you make permanent changes in exercise and/or eating, once you stop what you are doing to lose the weight, you typically regain the weight."

The Journal of the American Dietetic Association reported obesity is maintained primarily by a diet that is high in fat and added sugar and relatively low in fiber.1 Many times I tell my clients if they change the type of food they eat, they may not have to reduce the amount of food they eat. It seems prudent to state that a diet high in complex carbohydrates, i.e., fresh fruits, vegetables and fiber, and low in fat is the best bet so far.

Burning calories is far more effective than skimping on them to maintain weight. Thus enters the role of exercise. And strength training, or resistance training, seems to be a key player.

The heart of the matter

We know that physical activity is a good thing. Benefits are numerous and well documented, such as lowering blood pressure, lowering blood lipids, decreasing incidence of heart disease, maximizing oxygen uptake and increasing bone mass. There is evidence that also suggests exercise depresses appetite by stabilizing insulin and blood sugar levels, which could contribute indirectly to weight loss. Some experts think exercise helps with depression, too. What remains unclear is what type, for how long and at what level of intensity.

Inactive people can lose up to a half pound of muscle per year -- that's five pounds a decade of one of the body's most metabolically active tissues.2 Current research seems to suggest two effective approaches for weight control and/or changing the body's metabolism: strength training and aerobic exercise.

According to Dr. Jody Wilkinson, medical director of research at the Cooper Institute for Aerobics Research in Dallas, "Muscle is metabolically active tissue. The more lean muscle we have, the more calories we burn -- even when resting. Strength training increases BMR." Evans agrees: "You can change body chemistry through strength training, which gives an elevation in BMR by as much as l5 percent due to changes in lean muscle mass and protein turnover. It takes energy to build new muscle tissue. Changing body fat levels doesn't change metabolism."

According to Wayne Westcott, strength training consultant for the South Shore YMCA, Quincy, Mass., "The more muscle you have, the more calories you burn -- even at rest. A pound of muscle burns about 45 calories a day, whereas a pound of fat burns fewer than two calories a day."3 Keep in mind, too, that not all weight is created equal. A pound is a pound, whether it's bone, muscle or fat, but since a pound of muscle takes up less space than the same amount of fat, you can get smaller without actually losing weight.

The principle behind weight training is to add resistance to the body's natural movements so muscles get stronger. The American College of Sports Medicine guidelines call for performing a strength-training workout two to three times a week, with each session including eight to 12 different sets of exercises that work each of the body's major muscle groups. For best results, each of these sets should consist of eight to 12 lifts, or reps. Guidelines for aerobic exercise include an activity that keeps the heart beating at its training rate for 30 minutes or more, at least three times per week.

When asked about level of intensity, Evans says, "The theory that the lower the intensity of the activity, the more fat is burned, is an old one. Aerobic exercise does not raise BMR significantly, but it does burn calories. It's the number of calories burned that is important." Dr. Claude Bouchard, professor of exercise physiology at Laval University in Quebec, Canada, agrees. "It's still a valid goal to increase lean muscle mass and decrease body fat, but don't count on a higher metabolic rate to do it. Count more on calories expended through exercise to help you. Even walking briskly 30 minutes can raise the BMR to where it remains elevated for one hour afterward." Regardless of whether your body uses carbohydrates or fat during a workout, if you burn more calories than you take in, your body starts relying on its fat stores for energy to perform day-to-day activities between workouts.

When asked about "after burn," Stern says, "It's true that the body continues to increase metabolic rate after one stops exercising. The question is, how long does it last?" Wilkinson states, "It's better with aerobic exercise than strength training due to increased heart rate, increased oxygen consumption and increased calorie burning." Work in this area continues to remain controversial. Some studies report that metabolism stays elevated for 15 hours after high-intensity strength training. Others claim one hour, or a negligible increase. It is evident that every time one exercises, metabolic rate goes up temporarily, which translates into spent calories.

The set point theory is also being challenged. Research has shown that people who gain or lose weight experience metabolic changes that bring the body back to its baseline weight. But changes in diet or exercise could also alter the set point. Stern states, "It seems easier to raise [the set point] than to lower it. For sedentary people, becoming physically active lowers their set point. It's more important for them to just pick an activity they'll enjoy doing on a consistent basis."

Each person has a different metabolic rate. Aerobic exercise improves the body's ability to consume and use oxygen, which is vital for burning fuel, such as carbohydrates and fat. It raises heart rate and is important for cardiovascular fitness. Strength training is its complement, and a necessary adjunct to aerobic exercise. It indirectly increases BMR by increasing muscle.

Medical experts and researchers agree on this. They endorse a combination of strength and aerobic training as essential elements of a healthy lifestyle -- a lifestyle that should also include a nutritious diet -- as the best equation. Evans sums it up, "To boost metabolic rate, do strength training and eat a diet high in complex carbohydrates. Include aerobic exercise because of the calories expended. It's not one single event; it's all got to be a part of the lifestyle."

Small changes, big results

In spite of ongoing changes and continually evolving research, there are some worthwhile guidelines we can give our clients.

Consider the six-month plan. Those who shed weight a little at a time are often the most successful at keeping it off. The slower the change, the more time it has to become permanently incorporated into one's lifestyle. Also, it's easier for the body to adjust to a new set point. I flat out tell interested clients if they're still looking for a "quick fix," look me up when they're done. I'll still be here.

Examine food habits. Eliminate first the foods that won't be missed. It's easier to switch from potato chips to popcorn, ice cream to frozen yogurt, or soda to diet soda, than it is to give up cookies. Again, slow changes that do not leave the body feeling deprived are best.

Get moving. Perform aerobic and resistance training for long or short durations, with high or low intensity. Challenge clients to move their bodies. I tell them to think about "Moving their bodies forward into space."

Eat breakfast. Don't let clients tell you they're not hungry in the morning. Clients who use this excuse typically have binged the night before because they starved their body all day. Remember, restricting meals lowers metabolism.

Get advice from a nutritionist. Refer clients to a sports nutritionist for advice in food plans or binge eating, or other special dietary concerns.

Stop dieting, start eating. Switch over to "grazing" or eating smaller, but more frequent meals. It's easier on the vital organs, and research shows it can help improve metabolism

Pump up. Weight training improves one's overall fitness program, increases lean body mass and helps rev up basal metabolic rate.

Skim the fat. Shoot for about 20 to 30 percent of total calories from fat. You can actually train the body to prefer low-fat foods.

The slower, the better

Above all, remember each individual is different. Move slowly. Making small changes in diet and physical activity can make a huge difference in body chemistry.

REFERENCES

1. Journal of the American Dietetic Association, June 1994.

2. Prevention, August 1994, p. 59.

3. Westcott, Wayne. American Health, Jan/Feb 1995, p. 54.