Is BRI better than BMI? The new longevity metric men need to know

For decades, the Body Mass Index has labeled muscular men as overweight while missing the hidden risks in average-sized guys. Now, the Body Roundness Index offers a clearer picture of your shape, your visceral fat, and your future health.

“We have relied on BMI for too long, even though we know it is a blunt instrument. It cannot tell the difference between a powerlifter and a couch potato. BRI is exciting because it looks at the geometry of the body—specifically central roundness—which is where the real metabolic danger lies for men.”

Dr. Susan Carter, MD

The relationship

If you have ever walked out of a doctor’s office frustrated because a chart labeled you “obese” despite a rigorous gym routine, you have experienced the primary failure of the Body Mass Index (BMI). Developed over 150 years ago by a mathematician, not a physician, BMI is a simple calculation of weight divided by height. While useful for tracking populations, it often fails the individual male patient. It treats 20 pounds of iron-forged muscle exactly the same as 20 pounds of belly fat. This blind spot has led researchers to develop a sharper tool: the Body Roundness Index (BRI).

First proposed in 2013 by mathematician Diana Thomas and her team, BRI approaches the human body as a geometric shape rather than just a mass on a scale.^[1] It uses height and waist circumference—and sometimes hip circumference—to calculate how close your body shape is to a perfect circle. The score ranges from 1 to 16. A lower score indicates a leaner, more cylindrical shape, while a higher score indicates more “roundness.” Recent large-scale studies suggest that this measure of roundness is significantly more effective than BMI at predicting all-cause mortality and longevity.

The core connection between bri bmi longevity lies in what is being measured. BMI measures mass; BRI measures distribution. For men, this distinction is critical because of where we store fat. Evolution typically directs male fat storage to the abdominal cavity. This accumulation of tissue increases the body’s central radius. Research indicates that as your BRI score climbs, so does the volume of visceral adipose tissue—the deep, biologically active belly fat that surrounds the liver and pancreas.^[2] Unlike subcutaneous fat (the pinchable stuff under the skin), visceral fat drives systemic inflammation, making BRI a direct gauge of your internal metabolic environment.

How it works

The geometry of visceral fat

The mathematical formula for BRI calculates the eccentricity of the body’s shape. In geometry, eccentricity describes how much a shape deviates from being a circle. When a man gains weight around the midsection, his waist circumference expands relative to his height, making his torso more spherical. This geometric shift is almost exclusively driven by visceral adipose tissue (VAT).^[3] VAT is deep fat stored beneath the abdominal muscles, wrapping around vital organs.

Unlike fat on the arms or legs, visceral fat is vascular and metabolically aggressive. It rapidly releases fatty acids directly into the portal vein, which carries blood straight to the liver. This “portal theory” explains why central roundness is so closely tied to insulin resistance. The liver is flooded with free fatty acids, impairing its ability to manage blood sugar and cholesterol. Therefore, a high BRI score is essentially a mathematical marker for a liver under siege.

Inflammation and the cytokine storm

The reason researchers are linking bri bmi longevity so tightly is inflammation. Visceral fat cells are not inert storage lockers; they are active endocrine glands. They secrete inflammatory signaling proteins called cytokines, specifically Interleukin-6 (IL-6) and Tumor Necrosis Factor-alpha (TNF-alpha).^[4]

In men with high BRI scores, these cytokines create a state of chronic, low-grade inflammation throughout the body. This inflammation damages the endothelial lining (the inner walls) of the arteries, encouraging plaque buildup. While BMI might tell you that you are heavy, it misses this inflammatory activity. A man with a “normal” BMI but a high BRI (often called “skinny fat”) may have just as much vascular inflammation as a man with clinical obesity, putting him at significant risk for sudden cardiac events.

The testosterone trap

For men, body roundness creates a specific hormonal vicious cycle involving testosterone. Visceral fat contains high levels of an enzyme called aromatase. Aromatase converts testosterone into estradiol (a form of estrogen).^[5]

As a man’s BRI increases, his aromatase activity increases, causing his testosterone levels to drop and his estrogen levels to rise. Low testosterone facilitates further accumulation of visceral fat, which then converts more testosterone to estrogen. This feedback loop is why waist circumference is often inversely related to testosterone levels. BMI cannot track this dynamic. A bodybuilder with a high BMI likely has high testosterone; a man with a high BRI almost certainly has suppressed testosterone.

Identifying the TOFI phenotype

One of the most dangerous categories in preventative medicine is the TOFI phenotype: Thin Outside, Fat Inside. These are men who maintain a relatively low body weight and a healthy BMI, yet carry a disproportionate amount of fat in the abdominal cavity.^[6]

Because their arms and legs are slender, their total mass remains low. However, their BRI will be elevated because their waist-to-height ratio is poor. Studies show that TOFI men often face higher mortality risks than fit men with higher BMIs because they fly under the radar. They are rarely advised to make lifestyle changes until a metabolic crisis occurs. BRI exposes this hidden risk by focusing on shape rather than weight.

Conditions linked to it

Because BRI is a superior proxy for visceral adiposity, it correlates strongly with conditions rooted in metabolic dysfunction and inflammation. While high BMI is generally associated with joint issues and sleep apnea, high BRI is more specifically predictive of organ system failure and longevity.

Metabolic Syndrome: This cluster of conditions includes high blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol levels. Research indicates BRI is a more sensitive predictor of metabolic syndrome than BMI, particularly in men over 40.^[7]

Cardiovascular Disease (CVD): A 2024 study analyzing data from over 30,000 adults found that BRI showed a U-shaped association with all-cause mortality, with high scores strongly linked to cardiovascular death.^[8] The physical pressure of visceral fat on the kidneys can also drive hypertension (high blood pressure) independently of salt intake.

Type 2 Diabetes: The liver’s proximity to visceral fat makes it the first casualty of high body roundness. As the liver becomes fatty (steatotic), insulin resistance sets in rapidly. BRI tracks linearly with hemoglobin A1c levels, a long-term marker of blood sugar control.

Erectile Dysfunction (ED): ED is often the “canary in the coal mine” for vascular health. The inflammatory cytokines produced by visceral fat impair the release of nitric oxide, the chemical required for erections. Men with higher BRI scores report higher rates of ED, even when their BMI falls within the “overweight” rather than “obese” range.

Limitation Note: While BRI is promising, it is a relatively new metric compared to BMI. Long-term longitudinal studies spanning decades are still accumulating to fully cement clinical thresholds for specific populations.

Symptoms and signals

You do not always need a calculator to know if your body roundness is becoming a health liability. The male body gives clear signals when visceral fat accumulation is reaching a tipping point.

The belt buckle drift: You find yourself wearing your pants lower on your hips, under your stomach, rather than at your natural waist. This is a subconscious adjustment to accommodate increasing roundness.
Post-meal fatigue: Significant energy crashes 30 to 60 minutes after eating carbohydrates suggest insulin resistance driven by central adiposity.
The “hard” belly: A stomach that protrudes but feels firm to the touch (rather than jiggly) indicates visceral fat pushing against the abdominal wall, rather than subcutaneous fat sitting on top of it.
Rising blood pressure: A creeping increase in systolic blood pressure (the top number) often parallels an increase in waist circumference.
Reduced stamina: Feeling winded during activities that used to be easy, like climbing two flights of stairs, can signal that the extra visceral weight is mechanically restricting your diaphragm.

What to do about it

Improving your BRI score requires a targeted approach to reduce visceral fat. Unlike subcutaneous fat, which can be stubborn, visceral fat is highly responsive to lifestyle changes because of its high metabolic activity. Here is an evidence-based plan.

Step 1: Measure accurately

You cannot manage what you do not measure. To calculate your BRI, you need your height and an accurate waist circumference. Do not use your pants size—vanity sizing often makes a 36-inch waist actually measure 39 inches.

Stand and place a tape measure around your midsection at the level of your navel (belly button), not your hips. Exhale naturally and measure without sucking in. Use an online BRI calculator to determine your score. A score below 5 is generally considered healthy for most men, while scores consistently climbing above this threshold warrant intervention. Tracking this monthly is far more valuable than daily weigh-ins.

Step 2: Prioritize muscle-centric exercise

Cardio burns calories, but muscle burns fat around the clock. Resistance training increases insulin sensitivity by creating a “glucose sink”—muscle tissue that soaks up blood sugar so it doesn’t get stored as visceral fat.^[9]

Combine lifting with Zone 2 cardio (steady effort where you can still hold a conversation). This specific intensity improves mitochondrial efficiency, teaching your body to oxidize fat for fuel. Aim for three days of lifting and 150 minutes of Zone 2 cardio per week.

Step 3: Cut the liquid and processed carbs

Visceral fat feeds on fructose and rapid-digesting carbohydrates. High-fructose corn syrup and alcohol are metabolized primarily in the liver, promoting immediate fat storage in the abdomen. Eliminating sugary beverages, reducing alcohol intake, and focusing on fiber-rich complex carbohydrates creates the biological environment necessary for the liver to mobilize stored fat.

Myth vs Fact: The Belly Fat Edition

Myth: You can “crunch” away a high BRI.
Fact: Abdominal exercises build muscle under the fat, potentially pushing the belly out further. You must lose the fat through systemic metabolic changes, not spot reduction.
Myth: A “healthy” BMI means you are safe.
Fact: As discussed, a “skinny fat” man with a normal BMI but high waist circumference (high BRI) has a mortality risk comparable to an obese man.
Myth: It is just “aging.”
Fact: While metabolism slows slightly with age, the accumulation of visceral fat is driven by lifestyle and hormonal factors that can be reversed, not an inevitable consequence of getting older.

Bottom line

The debate of bri bmi longevity is settling in favor of roundness as the superior metric for men. While BMI has served as a general population tool, it fails to account for the unique physiology of the male body—specifically the danger of visceral fat and the safety of muscle mass. BRI provides a more honest look at your metabolic health. It ignores the weight of your broad shoulders and heavy legs, focusing instead on the central adiposity that threatens your longevity. If you want to live longer, stop obsessing over the number on the scale and start paying attention to the shape of your silhouette.

References

Thomas DM, Bredlau C, Bosy-Westphal A, et al. Relationships between body roundness with body fat and visceral adipose tissue emerging from a new geometrical model. Obesity (Silver Spring, Md.). 2013;21:2264-71. PMID: 23519954
Tchernof A, Després JP. Pathophysiology of human visceral obesity: an update. Physiological reviews. 2013;93:359-404. PMID: 23303913
Shuster A, Patlas M, Pinthus JH, et al. The clinical importance of visceral adiposity: a critical review of methods for visceral adipose tissue analysis. The British journal of radiology. 2012;85:1-10. PMID: 21937614
Fontana L, Eagon JC, Trujillo ME, et al. Visceral fat adipokine secretion is associated with systemic inflammation in obese humans. Diabetes. 2007;56:1010-3. PMID: 17287468
Cohen PG. The hypogonadal-obesity cycle: role of aromatase in modulating the testosterone-estradiol shunt–a major factor in the genesis of morbid obesity. Medical hypotheses. 1999;52:49-51. PMID: 10342671
Thomas EL, Frost G, Taylor-Robinson SD, et al. Excess body fat in obese and normal-weight subjects. Nutrition research reviews. 2012;25:150-61. PMID: 22625426
Rico-Martín S, Calderón-García JF, Sánchez-Rey P, et al. Effectiveness of body roundness index in predicting metabolic syndrome: A systematic review and meta-analysis. Obesity reviews : an official journal of the International Association for the Study of Obesity. 2020;21:e13023. PMID: 32267621
Zhang X, Ma N, Lin Q, et al. Body Roundness Index and All-Cause Mortality Among US Adults. JAMA network open. 2024;7:e2415051. PMID: 38837158
Srikanthan P, Karlamangla AS. Relative muscle mass is inversely associated with insulin resistance and prediabetes. Findings from the third National Health and Nutrition Examination Survey. The Journal of clinical endocrinology and metabolism. 2011;96:2898-903. PMID: 21778224