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Beyond weight loss, bariatric surgery was also effective at improving vascular outcomes, a new study found.

In a study of more than 300 adults with obesity, there was an average 17.5% loss of initial body weight during a roughly 6-month follow-up period after undergoing bariatric surgery, reported Noyan Gokce, MD, of Boston Medical Center in Massachusetts, and colleagues.

Starting at an initial baseline weight of 126 kg (278 lb) on average, these patients dropped down to an average weight of 104 kg (229 lb) at 6 months after surgery, the group wrote in .

On top of this weight loss benefit, these patients also saw a significant improvement in average endothelium-dependent flow-mediated dilation (FMD), indicating a significant improvement in macrovascular function (9.1% pre-surgery versus 10.2% post-surgery, P=0.001).

Patients also saw a significant increase in reactive hyperemia (RH), indicating an improvement in microvasculature following bariatric surgery (764% pre-surgery versus 923% post-surgery, P<0.001).

The researchers highlighted that both flow-mediated dilation and reactive hyperemia "have been clinically validated as independent predictors of cardiovascular risk."

Vascular function improved even after medications that are known to benefit endothelial function were discontinued, Gokce's group also noted. "[T]hus, the overall cumulative effect of weight loss on vascular function may have been moderated by stoppage of vasculoprotective agents owing to clinical reasons, such as normotension."

The researchers also pointed out that all patient subgroups, including Black and white patients, men and women, and those with metabolic syndrome, reaped the benefits of bariatric surgery in regards to weight loss and benefit on microvascular function.

Interestingly, even the subgroup of patients with so-called metabolically healthy obesity and low-grade inflammation (high-sensitivity C-reactive protein plasma levels >2 mg/dL) also saw a significant microvascular improvement following surgery. This particular finding suggesting a benefit of bariatric surgery for patients with otherwise metabolically healthy obesity touches "on a growing area of interest and controversy in the field that warrants further investigation," according to the researchers.

However, those with metabolically healthy obesity didn't see any significant improvement in macrovascular functioning.

Other clinical benefits of bariatric surgery included improvements in hip circumference, waist circumference, and high-density lipoprotein (HDL) cholesterol levels.

As expected, there was a benefit in HbA1c levels associated with the observed change in flow-mediated dilation. Looking at the entire cohort, there was a 0.5% (95% CI -0.95 to -0.05) drop in flow-mediated dilation associated with every 1-unit drop in HbA1c.

The population-based analysis included 307 patients with a BMI of 35 or higher who underwent bariatric surgery at Boston Medical Center from 2001 to 2019. Patients who had recent coronary syndromes, congestive heart failure, malignant neoplasm, systemic infection, acute illness, or pregnancy were excluded.

The bariatric surgery cohort mirrored clinical practice with a large majority being women (80%) and white (65%), limiting the generalizability of the findings. Average age was 42, and the average BMI of the cohort was 46.

Overall, 84% of patients opted for Roux-en-Y gastric bypass, while 16% had either sleeve gastrectomy or laparoscopic adjustable gastric band procedures.

The 74% of the cohort who were considered to have "metabolically unhealthy" obesity had to have at least three of the following clinical factors:

• Abdominal obesity (a waist circumference of at least 102 cm for men or 88 cm for women)
• Triglyceride level of 150 mg/dL or greater
• HDL cholesterol level under 40 mg/dL in men and under 50 mg/dL in women
• Blood pressure of at least 130/85 mm Hg or use of any hypertension medication
• Fasting plasma glucose level of at least 100 mg/dL

Those without at least three of these clinical factors were considered to have "metabolically healthy obesity."

Because the subset of patients with metabolically healthy obesity were the only group that didn't see both a significant macrovascular and microvascular benefit from surgery, Gokce's group suggested they "represent a mixed population that may benefit from more refined phenotypic classification."

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