Body mass index, or BMI, has long been the standard tool for assessing weight status and health risk. A calculation of your size that takes into account your height and weight, BMI is frequently used because it’s a quick, easy, and inexpensive measurement tool. Yet, it lacks any assessment of how much fat a person has or how it’s distributed throughout the body, both of which are key indicators of metabolic health. A recent study published in The BMJ analyzed different measures of body shape — more specifically, of central or abdominal fat — to determine which measures were most predictive of premature death.
Abdominal fat associated with higher risk of death
Researchers in this study analyzed the following measurements of central fatness: waist, hip, and thigh circumference; waist-to-hip ratio; waist-to-height ratio; waist-to-thigh ratio; body adiposity index (which incorporates hip circumference and height); and a body shape index (calculated from waist circumference, BMI, and height).
They found that a larger hip and thigh circumference (sometimes referred to as a pear shape) were associated with lower risk of death from all causes. All other measures, which indicated centrally located fat (sometimes called an apple shape), were associated with a higher risk of death. That is, the more abdominal fat a person has, the higher their risk of dying from any cause.
What do these results mean?
These findings tell us that not only does the total amount of body fat determine health risk, but also the location of that fat on a person’s body. Prior research has shown that abdominal obesity is more strongly associated than overall obesity with cardiovascular risk factors such as increased blood pressure, elevated blood triglyceride levels, and type 2 diabetes. Studies have shown it’s even linked to dementia, asthma, and some cancers.
Fat located around the abdomen, particularly visceral fat surrounding the liver and internal organs, is highly inflammatory and metabolically disruptive: it releases inflammatory molecules that contribute to insulin resistance, type 2 diabetes, and ultimately cardiovascular disease. In contrast, fat located at the hips and thighs is protective. These protective effects include an association with lower total cholesterol, LDL (or bad) cholesterol, triglycerides, arterial calcification, blood pressure, blood glucose and insulin levels, and higher sensitivity to insulin.
Taken together, these findings demonstrate the importance of using BMI along with measurements of abdominal fat to fully assess health risk.
What was missing from this analysis?
Researchers in the BMJ study looked at the data from multiple angles, breaking down the results by different categories such as sex, geographical location, smoking status, BMI, physical activity, and presence of disease such as diabetes and high blood pressure.
Notably, they did not analyze the relationship between abdominal obesity and mortality among different races or ethnicities. A 2005 study demonstrated that waist circumference was a better indicator of cardiovascular disease risk than BMI, and proposed different waist circumference cutoffs varying by race/ethnicity and gender for more accurately assessing that risk.
More recently, a 2015 statement from the American Heart Association warned about the misclassification of obesity (and cardiovascular risk) in different racial and ethnic groups. Specifically, current thresholds can lead to underestimating risk in Asian populations and overestimating risk in Black populations. As a result, people in these groups may inaccurately perceive their weight status, and doctors may fail to offer appropriate treatment options.
What can you do to reduce your risk?
The question everyone wants to know the answer to is: how can you decrease abdominal fat? Well, there’s bad news and good news. An older study looking at fat distribution among identical and fraternal twins revealed the bad news, which is that how your body stores fat is largely determined by genetics.
The good news is that abdominal fat responds to the same behavioral habits and strategies recommended for overall health and total body fat loss. Those strategies include the following:
Eat a healthy diet incorporating lean protein, fruits, vegetables, and whole grains.
Limit processed carbohydrates, and especially added sugars, which are sugars not occurring naturally in food.
Get adequate physical activity, at least 150 minutes per week of moderate-to-vigorous physical activity.
Get adequate restful sleep: for most adults that means seven to eight hours per night.
Limit stress, as it is correlated with the release of the hormone cortisol, which is linked to abdominal weight gain.
Racism and socioeconomic factors make fat loss harder for some
Although individuals have some control over the above lifestyle factors, we must acknowledge that there are systems-level factors that affect a person’s ability to access healthy foods, engage in regular physical activity, get adequate sleep, and reduce stress levels. These imbalances in access have long been linked with healthcare disparities.
This is particularly relevant as we enter 2021 — in the midst of the coronavirus pandemic, and exacerbated by social and political unrest in the United States. As a nation, we must confront these challenges and find systemwide solutions for reducing socioeconomic barriers and eliminating racism, in order to improve individual agency and ability to lead healthier lives.