In the battle of the bulge, it’s natural to focus on the number on the scale. After all, it’s the most accessible assessment tool we have — maybe next to how our pants fit — to figure out just where we stand weight-wise, whether for appearance’s sake, or for our health. While weight might be easy-to-understand terminology, however, it has its shortcomings, especially as an assessment tool. Mounting evidence points to the fact that, while height-versus-weight (also known as body mass index, or BMI) still has its uses, waist circumference is the better tool for assessing risk of diseases such as heart disease, type 2 diabetes, or cancer. Waist, definedOften misunderstood, waist circumference is a measure of your waist at its widest point — not where your pants fit. (Yes, gentlemen, I’m talking to you: Having your belly hang out of a pair of 36-inch pants does NOT mean that you have a 36-inch waist. Sorry.) Conversely, BMI, calculated as your weight in kilos, divided by the square of your height in metres (many websites will calculate it for you), does not take waist measurements or body type into account. That means that highly musculed individuals — think hockey players, boxers or MMA prize-fighters — can have a BMI that would be considered overweight, despite being at low risk for disease.When it comes to assessing disease risk, waist circumference seems to be particularly effective because it is highly related to the amount of visceral fat we possess. Visceral fat, which can roughly defined as the deeper fat that’s inside our body and around our organs, is different from the fat that we usually concern ourselves with, otherwise known as subcutaneous fat. While a few extra pounds of subcutaneous fat might keep our dream abs from popping, or our pipes from being shredded, it’s not a terribly effective indicator of disease risk. Yes, you heard it right: Whether your body fat percentage is 16% or 25% doesn’t tell you much about your likelihood of keeling over from a heart attack, despite what the magazines and gym membership-pushers might tell you. On other hand, a muffin top hanging over your previously-oh-so-perfectly-fitting jeans can be a more serious warning sign — and we’re not just talking about style points. Visceral fat — again, the fat that we are indirectly measuring when we measure waist circumference — is metabolically active and behaves much like an organ. Excess visceral fat leads to the secretion of mini hormones, known as cytokines, which in turn increase harmful inflammation, contributing to insulin resistance (the step before diabetes) and plaque formation (the precursor of a heart attack or stroke) over time.While we’ve had standard measures for waist circumference for some time — anything over 88 centimetres (34.5 inches) in women and 102 cm (40 inches) in men is considered abdominally obese — a new study has now given us a better idea of how much our waist affects our disease risk, even before we become overweight (BMI between 25 and 29.9), or obese (BMI greater than 30).Waist and riskThe study, published by researchers from the American Cancer Society in the journal Archives of Internal Medicine, examined the relationship between waist circumference and mortality among more than 100,000 men and women enrolled in the Cancer Prevention Study II (CPS-II) between 1997 and 2006. Over the 10-year period of the study, 9,315 men and 5,332 women died of all causes.When the researchers started digging through the data, they found some interesting relationships. In particular, they found that having a very large waist (defined as more than 120 cm, or 47 inches in men, or more than 110 cm, or 43 inches in women) more than doubled the risk of death compared with men and women with optimal waist sizes (less than 36 inches in men and 30 inches in women). But for those not on the high end of the scale, the study also found that, even among normal weight men and women, a four-inch (10 cm) increase in waist circumference increased the risk of death by 16% in men, and an eye-opening 25% in women. In other words, having a larger waist put these individuals at an increased risk of disease, even if their weight was in the so-called “normal” range. Similar patterns also held true for those with thicker waistlines in the overweight and obese categories.When it comes to interpreting this study, it’s important to keep in mind that the population was generally older (at baseline, the median, or mid-point, age was 69 years for the men, and 67 years for the women), and mostly white. Previous research has demonstrated that many non-white populations, including those of South and East Asian descent, are at an increased risk for disease at a relatively lower waist circumference. The bottom lineWhile BMI is still a fairly common tool for routine assessment of weight-related disease risk, waist circumference is at least as, or, as the results of this and other studies would suggest, more important. So next time you’re having your annual physical, take a deep breath and ask your doctor to measure your waistline. The news might not be great, but it could save your life.- Jennifer Sygo is a dietitian in private practice at Cleveland Clinic Canada (clevelandclinic.ca), which offers executive physicals, prevention and wellness counselling and personal health care management in Toronto.