The Truth About Mothers and their Daughters' Resemblance on BMI Charts

Is it true that mothers and their daughters' resemblance on BMI is a sure thing? It's easy to assume that a daughter might take after her mother's eating habits and have a similar BMI as her mother, for many reasons. But they might not be the reasons you'd think. But first, let's make it clear what BMI is.

BMI or body mass index is nothing more than the measure of a person's weight in relation to her height. A person's weight in kilograms is divided by a person's height in meters, squared (which is simply a person's height times itself—if I'm 1.5 meters tall, I would take 1.5 times 1.5). The resulting number is her BMI. A normal BMI is anything from 18.5 to 24.5, and 25 to 29.9 is considered overweight, with anything above that considered obese. A BMI below 18.5 is considered underweight. BMI is a good general measurement for most people, although very muscular people usually measure as overweight or obese because BMI doesn't distinguish between muscle weight and fat weight.

So, back to mothers and their daughters' resemblance on BMI, does it guarantee that a daughter will be overweight if her mother has a high BMI? Will a normal weight mother raise a normal weight daughter? Will the daughter be underweight if the mother is too skinny? While nothing is certain 100% of the time, there are some factors that push those answers more toward a yes than a no.

Genetics do play a part in a person's tendency toward staying thin or gaining weight. Hereditary factors like body type are impossible to change. Tendency toward a slow metabolism can be boosted by exercise, good nutrition and a healthy lifestyle, but genetics will help determine how easy or difficult keeping a high metabolism may be for a daughter.

The environment is a huge factor. When a mother is overweight, for example, and she generally cooks for the family, the family eat what she eats to a large degree. So it's easy to see why mothers and their daughters' resemblance on BMI is often very similar. Living with a person, especially someone with the influence a mother has on a daughter, also tends to shape a person's attitudes. So if the mother is very active, eats healthy and stays physically fit, it's more likely than a child, especially a daughter, will do the same. Conversely, a mother who is overweight, rarely gets exercise and doesn't seem overly concerned with weight loss or health is likely to bring up her daughter with the same outlook. In both cases, it's no surprise that their BMIs might be similar.

So not only do the attitudes about food and fitness filter down from mothers to daughters, the type of food eaten, and even the amount of food eaten, can filter down, too. Mothers and their daughters' resemblance on BMI charts is no coincidence, and only shows the need for families to be aware of their health and fitness even when children are small.

The Truth About BMI, Body Fat and Health

Though one of the most popular tools used today to determine whether someone is at a healthy weight or not is the BMI, body fat and lean muscle tissue don't figure into the equation. This has led many experts to discount BMI as an archaic measurement that isn't accurate for many people. What is BMI, and why is it a good measure for some, maybe, and completely wrong for others?

BMI, or body mass index, was created in the early 1800s by Adolphe Quetelet. Because of that, it's sometimes called the Quetelet index. It's nothing more than a way of comparing a person's weight to his or her height, and determining if his or her weight falls into a healthy and normal range. The BMI is still used today pretty much as it was when Quetelet invented it.

The formula for figuring BMI (body fat, bone and frame size, muscle and body type aren't included in that) is this: Take your height in meters squared (your height times itself) and divide your weight in kilograms by that number. For example, if I'm 5 feet tall, that's about 1.5 meters. To square that number, take 1.5 times 1.5. The result of that is 2.5. So if I weigh 120 pounds, that's about 54.5 kilograms. Divide 54.5 by 2.5 and I get 21.8 as my BMI. The normal weight range is from 18.5 to 24.9, so 21.8 is classified as a normal weight. Underweight is considered 18.5 and below, while overweight people will calculate a BMI of 25 to 29.9. A BMI of 30 or greater indicates obesity.

BMI, body fat and general health can all be used as signs of how fit a person is. But where general health is pretty self-explanatory and the percentage of body fat clearly shows whether a person gets enough exercise or not, BMI is a bit trickier.

People with a lot of muscle don't show accurate BMI readings. Because muscle weighs so much heaver than fat but takes up less space, a relatively small statured person can carry a lot of muscle weight without looking huge. BMI doesn't take that into account. Football players, professional wrestlers, bodybuilders, and virtually any athlete who has a lot of muscle is going to measure as overweight and even obese according to the BMI. So it's not accurate for them. Is it accurate for everyone else?

The answer to that is yes, and no. It depends on you. The BMI typically doesn't show an accurate result for children. And extremely tall or large-framed people will show overweight or obese classifications more easily because of the extra weight from their bones and muscles. So for very short, tall or muscular people, the BMI appears to not be a good tool.

There's also no distinguishing between men and women in the BMI. Body fat is more natural for women who are supposed to have more than men, so some sort of distinction in the measurement of the sexes would help the BMI's accuracy.

Learn the Secret of BMI Calculations

BMI calculations might seem like some esoteric and complicated process that you have no hope of figuring out. That's not true. BMI isn't magic or some scientific secret withheld by those in the know. If you've ever used a BMI calculator online, then you know that you put in your height and weight, and it cranks out special number. There's always a chart handy, or the website interprets it for you, and tells you whether you're underweight, normal weight, overweight or obese, all based on this single number. The website did the calculations for you, but you might be wondering just how it arrived at that number. BMI calculations are fairly simple once you understand the basic formula. But first, let's look at what BMI is and what BMI calculations are used for in the first place.

BMI is the measure of body mass. By comparing your weight and height, specifically dividing your weight by your height, squared, the BMI calculations give us a single number. Depending on where that number falls on a special scale, it tells you if you're underweight for your height, in the normal range, overweight, or obese.

BMI doesn't measure body fat, however, so often the number is wrong when it comes to athletes or very muscular people. Muscle weighs more than fat, so for them, BMI isn't an accurate measure at all. For most people, though, it's a very good estimate of weight in relation to height. So what BMI calculations allow us to arrive at that magic BMI number?

BMI calculations may seem complicated, but they're really not. At its most basic, the formula is kg/m2. Or your weight in kilograms divided by your height in meters, squared (your height in meters times itself). A person who's five-and-a-half-feet tall stands about 1.7 meters. Square that number (1.7 times 1.7) and you come up with 2.89. A person who weighs 150 pounds weights about 68 kilograms. So the BMI calculations to determine this person's BMI would be 68 divided by 2.89. The result of that is about 23.5.

A BMI of 18.5 or below indicates that an individual is underweight. The normal weight range is from 18.5 to 24.9. Overweight people will calculate a BMI of 25 to 29.9. A BMI of 30 or greater indicates obesity. So a person with a BMI of 23.5 is within his or her normal weight range, according to the BMI calculations.

If you don't want to convert feet and pounds to meters and kilograms, then you can use one of the other BMI calculations to figure your number. This person's new formula would be weight in pounds, 150, times 4.88, or 732, divided by height in feet squared (5.5 times 5.5) which is 30.25. Then divide weight by height squared (732 divided by 30.25) and the result is 24.1, very similar to the metric formula's result. BMI calculations can also be done by taking weight in pounds times 703, and dividing by height in inches, squared.