When my oldest son was in high school, we bought a Wii Fit. The first time he played it, he put his stats into the game (height, weight, age, gender) and his little MeWii guy went from medium size to a larger size. My son threw the remote away, said, “That’s stupid,” and never played it.
Body mass index (BMI), a calculation of height-to-weight ratio, has been used for many years by researchers and the medical community to determine health status and risks. But it’s imperfect. For example, athletes with greater muscle mass, like my son, will naturally weigh more. So, according to the BMI charts, he was “obese” for his height. But the reality was that his body fat percentage was low and his lean tissue, including muscle and bone, was high, giving him a healthy body composition.
BMI also cannot determine where body fat is distributed. We know that visceral or abdominal fat, the fat that lies deeper in the abdomen and surrounds vital organs, can put people at higher risk of illness and death when there is too much of it (some of it is necessary to help cushion the organs). But two people with the same BMI can have radically different constitutions. One may have more fat in the lower body (hips, legs, and butt) and the other may have more fat in the middle. So they weigh the same and are the same size, but because they carry fat to different places, whoever has more visceral fat could be at higher risk for chronic inflammation, heart disease, diabetes and of cancer.
Fortunately, researchers have caught on and there is now a newer, hopefully more accurate, way to determine health risks: the body curvature index (BRI). It is calculated using an equation integrating height, weight and waist circumference. And a study recently published in Open JAMA Network June 5, 2024 highlights the use of the BIS to determine the risk of dying prematurely, known as all-cause mortality.. Let’s see what this shows.
How was this study conducted and what did it show?
Researchers used data from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2018. NHANES is a series of surveys conducted every 2 years to monitor the public health of the U.S. population. Surveys are conducted via in-home interviews and mobile testing centers.
A total of 32,995 adults, half men and half women, with an average age of 47 years at the start of the study period, were used for this study. There was a racial and ethnic mix that included Mexican-Americans, non-Hispanic blacks, non-Hispanic whites, and other races and ethnicities: Native Americans, Alaska Natives, Native Hawaiians, Pacific Islanders, and non-Hispanic Asians.
Because researchers looked at mortality rates during the study period through December 31, 2019, mortality data was obtained through the Centers for Disease Control and Prevention (CDC) website and linked to the NHANES database.
Covariates – variables that may or may not affect or bias results – included age, gender, race and ethnicity, education level, poverty rate, smoking status, drinking status of alcohol (alcohol), family history of heart disease and family history of diabetes. Covariates also allow researchers to see if there are trends within any of the variables, such as whether age or education level affects the risk of disease or death.
Several statistical analyzes were performed on the data, before and after adjusting for covariates.
Because the BIS is so new, categories and ranges (such as low, normal, and high BIS) have not yet been established. For this reason, researchers had to create their own categories. Halfway through the study, researchers noticed a U-shaped association between BIS and deaths. From there, they formed various categories called quintiles, with Q1 being the lowest BIS and Q5 the highest. Q3 was designated as the reference group.
What they found was very interesting. Because higher amounts of visceral (belly) fat have been shown in previous studies to put people at higher risk of chronic disease and death, it is perhaps not surprising that these researchers have found that people who fell into the Q5 category, suggesting a high level of visceral fat. fat – were 50% more likely to die from any cause compared to the reference group (Q3).
But what might be unexpected was the finding that people who fell in the first trimester (suggesting a very low amount of visceral fat) were 25% more likely to die from any cause compared to to adults in the third trimester. This was especially true among people aged 65 and over.
Which give?
Researchers explain that a very low BIS has been associated with poor nutritional status, fatigue, reduced activity tolerance and muscle atrophy. In other words, people with a very low BIS tend to be malnourished and lose a lot of muscle. This leads to fatigue and the inability to be physically active.
Digging deeper, people in the fifth trimester tend to die more often from cardiovascular and metabolic disorders, like heart disease and diabetes, and from cancer. This was true even among those who were of “normal” weight, as you can be in a “normal” or “healthy” BMI or weight category and still have a higher proportion of fat in your waistline.
How does this apply to real life?
Although body shape and the location of fat deposits on your body are largely determined by genetics and life stage (menopause tends to shift fat storage toward the middle in women), you can Take certain steps to help keep visceral fat within a healthy range.
For example, there is evidence that a diet rich in fruits, vegetables, lean protein, healthy fats and fiber – essentially a Mediterranean diet – combined with physical activity, is a great combination to help combat visceral fat.
Lack of sleep and chronically high stress levels also promote the accumulation of abdominal fat. When stress is chronic, the stress hormone cortisol is constantly circulating in your body. Cortisol does several things, including promoting fat storage in, you guessed it, the abdomen.
When it comes to physical activity, a combination of aerobic exercise and strength training goes a long way in keeping visceral fat within a healthy range. It’s important to note that one-off training, like doing planks and sit-ups, will strengthen the core muscles but will not reduce fat in that area.
Interestingly, a study carried out in 2023 JMIR Public health and surveillance suggests that even “weekend warriors”, that is, people who do most of their physical activity during the weekend, showed reduced levels of abdominal fat, similar to those who were more regularly active.. This suggests that any activity counts, so if you’re not currently engaged in physical activity, simply start moving more and increase from there.
The essential
This 20-year study followed 32,995 American adults and found that those with very low and high amounts of abdominal fat had 25% and 50% higher rates of premature death, respectively. Following a healthy diet like the Mediterranean diet, engaging in regular physical activity, getting enough quality sleep, and reducing your stress levels all play a role in reducing visceral fat around your abdomen.