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Many people rely on the bathroom scale to tell them how healthy - or unhealthy - their weight is. But to get a more accurate picture of your health, there are other numbers you need to consider.
I'm not advocating throwing out the scale. Keeping tabs helps motivate people to stick to a weight-loss plan. It's also an important strategy to nip small weight gains before they accumulate. It's much easier to lose an extra three pounds than it is 10 or more.
As useful as the scale may be, it doesn't tell you everything you need to know about your weight. Determining how much body fat you have - and where you carry it - is important not only for weight control but also for fitness training and identifying health risk.
Body mass index (BMI)
If you're between the ages of 18 and 65, BMI is a height and weight formula that gives a pretty reliable snapshot of your body fat.
The easiest way to determine your BMI is to use an online calculator. (Google BMI calculator and you'll find lots of options.) It's calculated by dividing your weight (in kilograms) by your height (in metres, squared).
Doctors and dietitians use BMI to classify body weight and assess one's risk for disease. BMI values of less than 18.5 are considered underweight and increase a person's risk for conditions such as osteoporosis, nutrient deficiencies and eating disorders.
BMI values from 18.5 to 24.9 are defined as healthy or normal weight and linked with a lower risk of health problems.
As your BMI goes up, so does your risk for Type 2 diabetes, heart disease, high blood pressure, gallbladder disease, sleep apnea and some forms of cancer. If your BMI is from 25 to 29.9, you're classified as overweight; a BMI of 30 or greater is considered obese.
Keep in mind, though, that sudden or considerable weight gains or losses may also indicate health risk, even if this occurs within the normal BMI category.
(BMI can also be calculated for children and teenagers, but its interpretation depends on age and gender.)
The BMI is not without drawbacks. It doesn't tell you where you're carrying your body fat, which is important in determining obesity-related health risk.
It also doesn't distinguish between fat weight and muscle weight. Athletes and heavily muscled people may have a high BMI but very little fat (muscle weighs more than fat).
Body fat percentage
To prevent being misclassified based on BMI, some people prefer to have their body fat measured at the gym or their doctor's office.
Body calipers are used to measure skin fold thickness at various sites and the results are plugged into a formula to determine your overall percentage of body fat. If done by a skilled tester, this method is up to 98-per-cent accurate. (You can't do this yourself.)
Bioelectrical impedance measures body fat by sending a small electronic pulse through the body. (This is the type of body-fat analyzer available on some home scales.) The time it takes for the current to travel through your body is used to estimate your level of body fat. (The current passes through muscle and fat at different rates.)
Bioelectrical impedance measures can be thrown off by how hydrated you are, how much you've eaten and the temperature of your skin. It's best to take your reading under consistent conditions over time to detect changes.
Measuring your body fat every three to six months also lets you know the composition of your weight loss if you're dieting. A healthy weight-loss plan promotes fat reduction while preserving muscle.
According to the Canadian Society for Exercise Physiology, a body-fat measure between 17 and 28 per cent is acceptable for women and 12 to 21 per cent is acceptable for men.
Waist circumference
If you want to know where your fat is located, and how that fat is affecting your health, you need to measure your waist. Excess fat around the abdomen (apple shape) is associated with greater health risk than fat located on the hips and thighs (pear shape).
A waist circumference of 94 centimetres (37 inches) or greater for men and 80 cm (31.5 inches) or greater for women increases the likelihood of Type 2 diabetes, high blood pressure, elevated cholesterol, heart attack, stroke, metabolic syndrome and some cancers.
(Lower thresholds for waist circumference are recommended for Asian populations. Studies suggest health risk increases among many Asian populations at lower levels of body weight than in Caucasian populations.)
When it comes to health, not all fat cells are alike. Waist circumference is a good measure of visceral fat, the type of deep fat that packs itself around the organs and secretes chemicals that increase resistance to insulin and cause inflammation throughout the body. (Recent research suggests that hip and thigh fat may offer some unique protection against heart disease.)
Increased girth predicts a person's risk of disease and death better than BMI alone. For example, having a normal BMI and an increased waist circumference is a combination thought to double the risk of certain diseases. That's why the Canadian guidelines to assessing body weight use both BMI and waist circumference.
Measure your waist at the narrowest part of your trunk, about 2.5 cm (one inch) above your belly button, without holding the tape too tightly or too loosely. (Resist the urge to suck in your stomach.)
Waist-to-hip ratio (your waist measurement divided by your hip measurement) is another index of body-fat distribution, but some studies suggest it's less accurate than waist circumference at predicting health risk.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.
