Location, location, and location
How much is less important than where it’s located
With fat, location matters. Visceral fat occurs within the abdominal cavity. Subcutaneous fat occurs just beneath the skin. Researchers used data from 3,001 participants in the Framingham Heart Study Offspring and Third-Generation cohorts to determine links between these two types of fat and metabolic risk factors, such as type 2 diabetes. Compared to subcutaneous fat, visceral fat more strongly predicted most metabolic risk factors. For example, less that 1 percent of normal-weight women in the lowest quartile of visceral fat had the metabolic syndrome, compared to 8 percent of normal-weight women in the highest quartile of visceral fat. Visceral fat appears to be uniquely pathogenic.
Visceral fat, including fat in the liver and pancreas, supports metabolic derangement including increased risk of insulin resistance, excessive blood fats, high levels of small LDL-cholesterol particles, and low levels of HDL-cholesterol. Alas, measuring visceral fat requires expensive and time-consuming equipment. However, anyone can easily and reliably measure waist circumference and waist-to-hip ratio. Both measures reflect greater central obesity (belly fat), which is highly correlated with visceral obesity and increased risk of cardiovascular events.
Obesity predicts higher risk of cardiovascular disease. Yet, some studies have found that higher body-mass index (BMI) predicts lower risk of developing cardiovascular disease. Researchers typically evaluate obesity according to BMI values. But BMI does not adequately distinguish between different types of body fat and or between lean muscle mass, especially in normal weight people. A team of international researchers evaluated BMI, waist circumference, and waist-to-hip circumference ratio as predictors of mortality of people with cardiovascular disease. Waist circumference and waist-to-hip ratio were better predictors of mortality risk than was BMI. In fact, the risk of mortality declined as BMI increased! Waist circumference and waist-to-hip ratio reflect central obesity, which is highly correlated with visceral obesity, which predicts increased risk of insulin resistance, excessive blood fats, high levels of small LDL-cholesterol particles, and low HDL-cholesterol. All of these outcomes predict increased risk of cardiovascular events.
Other researchers used data from 15,185 participants with an average of 45 years in the third National Health and Nutrition Examination Survey. Results showed that people with normal weight and central obesity had the highest risks of dying over 14 years of follow-up. Men participants with normal-weight (BMI of 22) and central obesity had an 87 percent higher risk of dying during follow-up compared to men with normal-weight BMI and no central obesity. Women participants with normal weight and central obesity had a 48 percent higher risk of dying during follow-up compared to women with normal weight and no central obesity. Both men and women who were overweight or obese (as measured by BMI) and who had central obesity showed even higher risks of dying during follow-up. Location of body fat matters with respect to risk of dying.
In 2010, the American Heart Association published the Life’s Simple 7 metrics to assess and promote cardiovascular health. The seven factors included 1) smoking, 2) physical activity, 3) body-mass index, 4) diet, 5) total serum cholesterol, 6) blood pressure, and 7) fasting blood glucose. Subsequent research suggested that three of the metrics should be revised to better predict cardiovascular and cancer mortality. Waist-to-hip ratio replaced BMI. The Healthy Eating Index-2000 provided the diet score. The ideal blood pressure declined from 130/80 mm Hg to 120/80 mm Hg. For both versions of Life’s Simple Seven, scores ranged from 0 (worst) to 7 (best).
Researchers used data from the National Health and Nutrition Examination Surveys to evaluate the revised Life’s Simple Seven. Compared to participants with revised scores of 0 or 1, participants with revised scores of 5 or more had 54 percent lower risk of all-cause mortality, 58 percent lower risk of cancer mortality, and 63 percent lower risk of cardiovascular mortality. Interestingly, overweight participants (BMI less than 30) but without central obesity (waist-to-hip ratio less than 0.9 for men and 0.8 for women) had lower risk of all-cause and cardiovascular disease mortality. This finding supports previous studies showing that fat’s location is a better predictor of cardiovascular disease than its amount. The revised Life’s Simple Seven provided more information than the original Life’s Simple Seven, especially for cancer mortality. Alas, only about 1 percent of participants achieved ideal values of the revised Life’s Seven Simple metrics.
Public health guidelines for obesity prevention are derived from BMI values. BMI does not, however, account for body shape or body fat distribution. As noted above, persons with normal BMI can have central obesity, namely excess belly fat accumulation. A recent study investigated the relative risks of all-cause and cause-specific mortality for 156,624 post-menopausal women. There were six combinations of BMI and belly fat (measured as waist circumference). Compared to normal weight women with normal waist circumference, normal weight women with high waist circumference (more than 88 cm) had a 31 percent higher risk of all-cause mortality over an average follow-up of 18 years. This risk level accounted for a host of potentially confounding factors. High waist circumference consistently predicted higher risk of all-cause, cardiovascular-related, and cancer mortality, regardless of BMI. Overweight or obesity, coupled with normal waist circumference, consistently predicted lower risk of death. Thus, the current public health emphasis on losing weight to reduce obesity (as defined by BMI) and improve health may be misdirected.
Recent evidence suggests that BMI may not best reflect the adverse health consequences of obesity. Japanese researchers used cross-sectional data to determine if central obesity (measured by waist circumference to height ratio) predicted risk of cardiovascular disease risk factors compared to general obesity (defined by BMI). The study included 117,163 men and women participants with an average of 50 years in the All Japan Labor Welfare Foundation. Compared to normal-weight participants with no central obesity, participants with normal weight and central obesity had significantly greater risks of hypertension, excess blood fats, and diabetes, after adjusting for age, weight, and smoking status. Central obesity predicted the presence of cardiovascular disease risk factors better than did general obesity for both men and women.
If you have normal body weight but substantial belly fat, you’ll probably be healthier if you lose most of your belly fat. How to do that? Eat Better, Keep Moving, and Defuse Chronic Stress.
