Every afternoon, Georgetown Medical Center professor Dr. Harry Preuss walks for an hour, going outside if it is sunny or trotting up and down the halls if it is cloudy. He wears a pedometer to count his steps, aiming for 15,000 steps by the end of the day, or about 7.5 miles, according to his estimates.
The professor of physiology, medicine and pathology has been exercising for the past 10 years, going for daily walks and lifting weights two to three times a week in his home gym for the past four to five years.
“It’s not only for young males who want to look like Adonis, but it’s for older men and women,” says Dr. Preuss, co-author of “The Natural Fat-Loss Pharmacy, Drug-Free Remedies to Help You Safely Lose Weight, Shed Fat, Firm Up, and Feel Great.”
“If you can keep your muscles up and not develop sarcopenia, or lack of muscle, you can remain independent and live mobile a lot longer,” he says.
Regular aerobic exercise and resistance training, along with a calorie-restricted diet, are keys to building muscle and losing fat, according to metro-area physicians, nutritionists and dietitians.
“You need to focus on burning calories, not fat,” says Shelley Goldberg, a registered dietitian and certified personal trainer. She is director of nutrition communication for the International Food Information Council, a provider of science-based information on food safety and nutrition based in Northwest.
A pound of fat is made up of 3,500 calories of stored energy, Ms. Goldberg says. Cutting back by 500 calories a day, or increasing exercise to burn 250 calories and reducing caloric intake by 250 calories can eliminate 1 pound of fat over the course of a week, she says. Losing 1 to 2 pounds a week is the maximum weight loss that can be sustained, she says.
“I wouldn’t recommend more than that. A lot of people tend to gain it back,” she says.
Performing 30 minutes of low-intensity aerobic exercise burns about 200 calories, with 120 calories, or 60 percent, coming from stored fat, Ms. Goldberg says, citing the American Council on Exercise, based in San Diego. With high-intensity exercise, 400 calories are burned in 30 minutes with 140 calories, or 35 percent, coming from fat, she says.
“While it is true that a higher proportion of calories burned during low-intensity exercise come from fat, high-intensity exercise still burns more calories from fat in the final analysis,” she says.
Researchers believe body fat is stored in adipose cells, which expand with weight gain, or in an increase in the number of fat cells, says registered dietitian Denise Feeley, a nutritionist at MedStar Research Institute in Southeast.
“The excess energy, through a series of chemical reactions, creates body fat,” Ms. Feeley says.
Excess calories are stored in adipose tissue in the form of triglycerides, a concentrated source of energy, says registered dietitian Meg Martin, clinical nutrition manager at Inova Alexandria Hospital.
“Stored fat can give us energy when we’re not taking in enough calories,” Miss Martin says.
Fat, carbohydrates and protein are the three nutrients that give the body energy, says Wayne Miller, professor of exercise science at the George Washington University Medical Center in Northwest. He holds a doctorate in exercise physiology.
Excess fat is stored as body fat, while excess carbohydrates can be stored in limited amounts in the liver and muscles, Mr. Miller says. Excess protein cannot be stored, he says.
“The thing about fat is, it can be stored in unlimited quantities,” Mr. Miller says.
Each gram of fat has 9 calories, compared to 4 calories for each gram of carbohydrates or protein, Miss Martin says.
Fat and carbohydrates from what has been consumed and stored are the body’s preferable energy sources, not protein, Miss Martin says. In a starvation diet, after stored carbohydrates are burned up, the body can start burning protein in muscle tissue to produce energy, she says.
“We use some protein for energy, but we want most of it to lay down or repair muscle tissue,” Miss Martin says.
The body uses energy from calories consumed before using stored glycogen and fat, she says. During moderately paced exercise over a prolonged period, the body uses muscle glycogen, liver glycogen and some fat, she says.
“Over an hour, the percent of energy you use from fat will go up,” Miss Martin says.
Quick weight loss forces the body to hold on to calories and maintain fat reserves in case of an emergency, slowing metabolism, Ms. Goldberg says.
Metabolism — a measure of how many calories the body burns while at rest — is based on four factors, height, weight, gender and muscle mass, Ms. Goldberg says. As a general rule, taller people require more calories to function; heavier people require more calories to move; men burn more calories than women; and muscle tissue is more metabolically active than fat tissue, she says.
“The best way to have an efficient metabolism is to eat throughout the day,” Miss Martin says. “Your metabolism works much better. It knows it’s being nourished properly.”
Dieting slowly will not cause an abrupt lowering of metabolism, Dr. Preuss says.
Dr. Preuss recommends watching calories and food portions and eating smaller, more frequent meals. Carbohydrates, more than fats, need to be limited, particularly sugars that can be broken down rapidly and absorbed by the body, he says.
Losing weight quickly is relatively easy for the first few pounds, but then the body plateaus and goes into starvation mode to try to maintain its fat reserves, Dr. Preuss says.
“You gained the weight over a long time, so you have to lose it over a long time,” he says.
Dramatic weight losses are difficult to maintain as a lifestyle change, Mr. Miller says.
“The most important thing is consistency,” he says. “Small changes over a long period of time that can be consistent are the best bet. That’s the way we gain our fat.”
In addition, quick weight loss, followed by a return to earlier eating habits, causes the weight to be gained back, plus possibly more, Miss Martin says. Muscle tissue may have been broken down for energy, reducing lean body mass and thereby lowering resting metabolic rate, she says.
“When people tend to lose weight quickly, they tend to sabotage their metabolism,” Miss Miller says.