|
Healthy Weight
Article by The Harvard School of Public Health
continued -
What's a Healthy Weight?
Although nutrition experts still debate the precise limits of what constitutes a healthy weight, there's a good working definition based on the ratio of weight to height. This ratio, called the body mass index (or BMI for short), takes into account the fact that taller people have more tissue than shorter people, and so tend to weigh more.
Dozens of studies that have included more than a million adults have shown that a body mass index above 25 increases the chan
Calculate your BMI
With a calculator handy (or pencil and paper if you like multiplication and long division), you can determine your body-mass index like this: Divide your weight in pounds by your height in inches. Divide the answer by your height in inches. Multiply the answer by 703.
For a person who is 5'8" (68 inches) and weighs 172 pounds, that would be 172÷68÷68x703, or a shade over 26.
Chances of dying early, mainly from heart disease or cancer, and that a body mass index above 30 dramatically increases the chances. Based on this consistent body of research, a healthy weight is one that equates with a body mass index less than 25. By convention, overweight is defined as a body mass index of 25 to 29.9, and obesity is defined as a body mass index of 30 or higher.
Nothing magical happens when you cross from 24.9 to 25 or from 29.9 to 30. These are just convenient reference points. Instead, the chances of developing a weight-related health problems increases across the range of weights
Muscle and bone are more dense than fat, so an athlete or muscular person may have a high body mass index, but not be fat. It's this very thing that makes weight gain during adulthood such an important determinant of weight-related health--few adults add muscle and bone after their early twenties, so nearly all that added weight is fat.
Waist Size Matters, Too
Some research suggests that not all fat is created equal. Fat that accumulates around the waist and chest (what's called abdominal adiposity) may be more dangerous for long-term health than fat that accumulates elsewhere. Some studies suggest that abdominal fat plays a role in the development of high blood pressure, high cholesterol, high blood sugar, and heart disease. It's also possible, of course, that abdominal fat isn't worse than fat around the hips or thighs, but instead is a signal of overall body-fat accumulation that weight alone just doesn't capture.
Measuring your waist is easy, if you know exactly where your waist really is. Wrap a flexible measuring tape around your midsection where the sides of your waist are the narrowest. This is usually even with your navel. Make sure you keep the tape parallel to the floor.
An expert panel convened by the National Institutes of Health concluded that a waist larger than 40 inches for men and 35 inches for women increases the chances of developing heart disease, cancer, or other chronic diseases. Although these are a bit generous they are useful benchmarks.
Waist size is a simple, useful measurement because abdominal muscle can be replaced by fat with age, even though weight may remain the same. So increasing waist size can serve as a warning that you ought to take a look at how much you are eating and exercising.
Keeping Things Level
Middle-aged spread is the source of millions of New Year's resolutions. Gaining weight as you age increases the chances of developing one or more chronic diseases. In the Nurses' Health Study and the Health Professionals Follow-up Study, middle-aged women and men who gained 11 - 22 pounds after age 20 were up to three times more likely to develop heart disease, high blood pressure, type 2 diabetes, and gallstones than those who gained five pounds or fewer. Those who gained more than 22 pounds had even larger risks of developing these diseases.
Relation between body-mass index up to 30 and the relative risk of type 2 diabetes, hypertension, coronary heart disease, and cholelithiasis in the Nurses' Health Study among women initially aged 30 to 55 years followed for up to 18 years and in the Health Professionals Follow-up Study among men initially aged 40 to 65 years followed for up to 10 years.
What Causes Weight Gain
Whether or not your weight changes depends on a simple rule:
Weight change = calories in - calories out
If you burn as many calories as you take in each day, there's nothing left over for storage in fat cells and weight remains the same. Eat more than you burn, though, and you end up adding fat and pounds.
Many things influence what and when you eat and how many calories you burn. These turn what seems to be a straightforward pathway to excess weight into a complex journey that may start very early in life.
*Genes: Some people are genetically predisposed to gain weight more easily than others or to store fat around the abdomen and chest. It's also possible that humans have a genetic drive to eat more than they need for the present in order to store energy for future. This is called the thrifty gene hypothesis. It suggests that eating extra food whenever possible helped early humans survive feast-or-famine conditions. If such thrifty genes still exist, they aren't doing us much good in an environment in which food is constantly available.
*Diet: At the risk of stating the obvious, the quantity of food in your diet has a strong impact on weight. The composition of your diet, though, seems to play little role in weight-a calorie is a calorie, regardless of its source.
*Physical activity: The "calories burned" part of the weight-change equation often get short shrift. The more active you are, the more calories you burn, which means that less energy will be available for storage as fat. Exercising more also reduces the chances of developing heart disease, some types of cancer, and other chronic diseases. In other words, physical activity is a key element of weight control and health.
|
|
|
