HAVE you ever noticed that some people eat so much and stay so thin? We have all known people who eat a lot and stayed thin. We may have heard that their metabolisms were high, but what exactly does that mean? We need to understand how our metabolisms work.
In my previous column, I discussed where calories come from and how they function as our energy source, how these are calories used and about exercise. Calories are used in three ways: digesting food, physical activity and basal metabolic rate (BMR).
The percentage of your total calories each of these uses remains fairly constant: digestion uses 10 percent, physical activity uses 25 percent and basal metabolic rate uses 65 percent. While you can’t change the percentage of each of these uses, you can change your calorie demand, and thus, alter the total calories required by your body. A person who consumes 1,000 calories a day uses 10 percent, or 100 calories, to digest that food, and a person who consumes 3,000 calories uses 10 percent, or 300 calories, to digest that food. While digestion stays at 10 percent, the number of calories used to burn the food you eat increases from 100 to 300 calories by eating more. You need to find a way to burn more calories without eating more.
The second use of calories is physical activity. Getting out of your chair and going to the refrigerator is physical activity; so is going for a walk. The number of calories you use depends on your body weight and time. A person who weighs 200 pounds and walks for 10 minutes uses more calories than a person who weighs 150 pounds and walks for 10 minutes. All of your physical activities in a day use only about 25 percent of the total calories you consume. This means the physical activity from driving to the store, washing dishes, changing the channel on the television–everything–only accounts for 25 percent of your total calories, and this even includes that 15 to 30 minutes of aerobic exercise three to five times a week.
Pay attention, because here is one of the secrets of permanent weight loss and control. Approximately 65 percent of the calories consumed in a day are used to supply the energy for the basic work of the body’s cells to maintain life. This is energy used to keep the heart beating, the lungs breathing, all cells conducting activities, and the nerves generating their continuous streams of electrical impulses. Basically, it’s all the functions that support life 24 hours a day, even while you sleep. This is called the metabolic rate.
Your BMR can be measured in a laboratory while you are lying down and not digesting any food. By eliminating digestion and physical activity, electronic instruments can measure your calorie expenditure that is needed to support life. How can two people who are the same age, sex, height and weight burn different amounts of calories while they are just lying down? How can some people eat so much and stay thin? How does a person obtain a high BMR? What’s the secret?
The key is the amount of lean body tissue or fat-free mass you have. Even when we sleep, lean tissue is more active metabolically than fat tissue. A person with lean tissue instead of fat tissue burns more calories and therefore, gets to eat more calories.
If you exercise and burn 200 calories every other day, the important point to remember is that you are keeping your muscles lean. Consequently, these muscles are using more calories the rest of the day, even at night. It’s the calorie demand of their BMRs that keeps fat people fat and thin people thin. Overweight people with lots of fat tissue will have a low calorie demand for their BMRs. On the other hand, people with more lean tissue will have a high calorie demand for their BMRs.
And as you now know, your BMR accounts for 65 percent of your total calories.
The good news is that you can change your BMR. An overweight person can get thin, but it takes knowledge, commitment and time. The longer you have been overweight, the longer it takes to become thin. But it is easy, once you have the know-how. You should not try to lose too much weight too fast. Fasting and dieting lower your basal metabolic rate, which is the opposite of what you want to do. Your body thinks there is a food shortage, and it slows down your BMR so you can survive on fewer calories. Although you may lose a lot of weight, much of it will be muscle and not fat. If you decide to lose a lot of weight in a hurry, don’t throw away your old clothes, because the fat will be back. Many people have done exactly the same thing. When they lost a lot of weight in a short time, they lost muscle along with fat and their BMR slowed down. If you lose weight gradually (½ to 1 pound a week), you have two important advantages. First, your body doesn’t think there’s a food shortage, and your BMR doesn’t slow down. Second, you lose fat and not muscle. If you add moderate exercise, your muscles become leaner, thereby raising your BMR. A higher BMR means you get to eat more.
If you’re overweight, I suggest you ask yourself two questions: Do fewer than 30 percent of my calories come from fat? Do I exercise the equivalent of a 30-minute walk three to five times a week? The starting point for weight loss and control is a resounding “yes” to both of these questions. Please don’t fall victim to the celebrity who advertises some weight-loss program or product. You’re smart—give yourself credit. If it sounds dumb or too good to be true, then it is. By now, you realize that when you lose weight, you could be losing water, muscle or fat. Only when you understand how to lose fat can you achieve permanent weight control.
