Body mass index is a way of measuring your body’s mass, a statistical measurement that gives an estimate of a healthy body weight based on the height of a person.
Overall, it gives you and your doctor a good idea of how you stand weight-wise.
In general, for an adult female (males have slightly higher BMI numbers), if you have a BMI of less than 18.5, you are considered underweight; 18.5 to 24.9 means normal weight; 25 to 29.9 means overweight; and over 30 is considered obese.
To determine your BMI, take your weight in pounds and your height in total inches.
Then multiply your weight times 703, and divide that number by your height squared.
For example, if you are 5 feet, 4 inches tall (or 64 inches tall) and weigh 133 pounds, the calculation would be as follows: 133 x 703 = 93,449; 64 inches squared = 4,096; divide 93,449/4,096 = 22.83, your BMI is in the normal range.
What are some of the health risks of having a high BMI?
There are numerous health risks if a person has a high BMI, or body mass index, meaning over 30. Risks include hypertension, dyslipidemia (for more about dyslipidemia and diabetes, see the chapter “How Diabetes Affects the Circulatory System”), type 2 diabetes, cardiovascular disease, stroke, gallbladder disease, osteoarthritis, sleep apnea and respiratory problems, gout, and even certain types of cancer, such as endometrial, breast, and colon cancers.
Is a high BMI the only factor in obesity?
No.
Health care professionals also cite genetic, environmental, psychological, and underlying medical problems, all of which may be factors that lead to obesity.
Underlying medical conditions may include hypothyroidism, Cushing’s syndrome, depression, and certain neurological problems that can lead to overeating.
Drugs, such as steroids, used to treat certain medical conditions may cause weight gain, too.
Scientific study has also indicated that obesity may be linked to heredity, but many researchers note that in terms of a “family unit” that shares the same basic diet, it is often difficult to separate genetics from environmental factors.
A simple calculation based on your weight and height will give you your BMI and tell you whether you are at a healthy weight or not.
Why are many doctors concerned about BMI in terms of diabetes?
Health care professionals are usually concerned if a person’s BMI is too high, which often indicates that the individual is very overweight or obese. In addition, many studies have found that a person’s BMI is strongly and independently associated with the risk of being diagnosed with type 2 diabetes.
What is an example of a good BMI for a certain height?
Depending on your height, which is usually considered to be a constant, you can also determine what weight range will send you into another BMI category. For example, here are the weight ranges, the corresponding BMI ranges, and the weight-status categories for a sample height of a man who is 5 feet, 9 inches:
BMI for 5'9" Tall Male
Weight Range
BMI
Weight Staus
124 lbs. or less
Below 18.5
Underweight
125 lbs. to 168 lbs.
18.5 to 24.9
Normal
169 lbs. to 202 lbs.
25.0 to 29.9
Overweight
203 lbs. or more
30 or higher
Obese
STUDIES IN OBESITY
Do researchers believe that obesity is inherited?
To date, researchers studying obesity genetics have identified more than 30 candidate genes on 12 chromosomes associated with body mass index, or how much weight we carry around (for more about body mass index, see this chapter).
For example, in 2007, the first “fat mass and obesity-associated” gene (or FTO) was found on chromosome 16; it’s estimated that people who have this gene variant carry a 20 to 30 percent higher risk of obesity.
Another obesity-associated gene is located on chromosome 18.
But as many researchers mention, even when the genes are found, they only account for a small part of the gene-related susceptibility to obesity.
According to Harvard University’s School of Public Health, recent research shows that genetic factors identified so far in obesity make only a small contribution to a person’s obesity risk, and that our genes are “not our destiny.” In other words, many people who do have the so-called “obesity genes” do not necessarily become obese or even overweight, and often can counteract potential overweight problems owing to genes with exercise and healthful eating habits.
How reliable is BMI as a health indicator?
F or several reasons, not everyone thinks that the BMI is a person’s best indicator of health.
For example, although the connection between the BMI number and the fatness of a person is fairly strong, the numbers all vary by gender, race, and age; for instance, at the same BMI, older people (on average) tend to have more body fat than younger adults, and highly trained athletes may also have a high BMI, but it is more because of muscles than body fat.
Another objection is that the BMI is only one factor related to risk for certain diseases.
Thus, some organizations look at other factors to understand a person’s likelihood of developing overweight- or obesity-related diseases.
For example, the National Heart, Lung, and Blood Institute guidelines recommend looking at two other factors: A person’s waist circumference (because abdominal fat is often a predictor of risk for obesity-related diseases) and other possible risk factors a person has for diseases associated with obesity (for example, high blood pressure or physical inactivity).
Why are carbohydrates the center of a debate about type 2 diabetes?
Some researchers believe that it is actually carbohydrates in our diets that have made many people overweight and eventually obese, both of which conditions can lead to type 2 diabetes. They believe that insulin resistance in many people is caused by the pancreas’s “wearing out,” as it sends out more and more insulin, so more sugar is stored as fat, which leads to obesity.
The researchers’ solutions seem drastic to some, as they often contradict some commonly “accepted” dietary guidelines.
The researchers believe that several foods should be replaced in the diet, as they cause such rapid sugar spikes after eating.
These foods include whole grains (which raise the blood sugar drastically after ingestion and can be replaced with such flours as coconut or almond), potatoes, and sugar.
This way, the body will not be flooded with sugar followed by insulin and, thus, will lower fat stores in the body.
The researchers also believe that a person with type 2 diabetes, or even prediabetes, should eat more protein and fats instead of most carbohydrates.
This is because proteins, especially fats, do not cause a spike in blood glucose levels after eating.
Overall, the researchers’ message is that most (especially Western) diets have not cut back on carbohydrates; they also stress that obesity may be linked not to which carbohydrates a person eats but to how much the person eats for his or her particular body. They also note that much of the information about treating diabetes tends to mention the medications as opposed to such alternatives as maintaining a health lifestyle. They do admit, too, that some people do have a genetic predisposition to type 2 diabetes, but their main concern is that along with the increase in type 2 diabetes has come an increase in obesity.
Is type 2 diabetes a problem for low-income people?
Yes, in many cases, type 2 diabetes is a major problem for low-income people, and it can sometimes afflict entire families. A recent study found that at the end of a month, low-income people are admitted to hospitals with low blood sugar more than people with higher incomes. It is thought that this is because without money, the low-income people cannot buy enough to feed their families. This lack of stable access to food can cause a person to have unstable blood glucose levels.
OBESITY RESEARCH AND STATISTICS
What is the “obesity paradox”?
In the past decade or so, researchers have noticed that there are people who are not obese or overweight but still develop diseases most often associated with excess weight.
The phrase “obesity paradox” refers to these normal-weight people who are not obese but still develop diseases such as type 2 diabetes, and those diseases seem to affect them more than they do obese people with diabetes.
In one 2016 study from the Journal of the American Medical Association, it was found that normal-weight people who develop type 2 diabetes often have double the risk of dying from heart disease and other causes over people who have type 2 diabetes and are overweight.
The paradox comes from the idea that excess weight can “protect” certain people, though the opposite is more often true.
The researchers do not suggest that people become overweight to stave off certain diseases like type 2 diabetes.
This is because statistics show that around 85 percent of people who do develop type 2 diabetes are overweight or obese.
What they believe is that something other than weight gain is causing the onset and severity of type 2 diabetes in these “normal-weight” people.
Some suggest it may be certain conditions not yet researched as much, such as the amount of fat a person carries around his or her waist.
Another suggestion is that such conditions for these people may not be the amount of fat itself but how the person stores it in the body.
Still another study points to hormones that tell the brain when to eat or when the person has had enough to eat.
What is thought to contribute to diabetes even though it is meant to help?
F ood banks have been a good source of foods for people who can’t always afford to pay for groceries.
But in 2014, the United States’ largest hunger-relief organization, Feeding America, reported that a third of the 15.5 million households they served reported at least one household member had diabetes.
There seem to be several major reasons.
For example, if a person (and/or family) has inconsistent access to food, it can worsen a diabetic condition.
In addition, many times, inexpensive foods are bought by people trying to stretch their paycheck, with most of those foods being low in fiber and rich in carbohydrates and fats, all of which contribute to obesity and can lead to type 2 diabetes.
There are also food banks that cannot afford (or do not offer) many healthful choices.
Thus, many people who use those food banks must choose prepackaged or fattening foods that can contribute to obesity, and potentially lead to diabetes.
What study found a possible connection between certain chemicals in the body and obesity?
In a study presented in 2007, researchers found that many obese people in the study actually had higher amounts in their systems of leptin, a hunger-suppressing hormone, but in most cases, the participants’ systems were also resistant to leptin.
This hormone is released by fat cells and travels through the bloodstream to the brain.
In general, the more fat a person has on his or her body, the more leptin is released.
But when a person’s fat level is low, which means the leptin levels are low, it causes the brain to increase the person’s appetite, so he or she eats more and gains weight.
The researchers also discovered that obese people had suppressed ghrelin levels, a chemical the stomach secretes when it is empty to tell the brain that it’s time to eat. Both leptin and ghrelin may contribute to a person’s propensity to eat too much at meals, and they are thus associated with hunger and craving, along with the possibility of contributing to obesity. They may also contribute to the reasons behind the “obesity paradox” (see above), in which the fat, brain, and leptin do not respond correctly, and many times lead to type 2 diabetes without the person’s being obese.