The skyrocketing popularity of GLP-1 receptor agonists has transformed the weight-loss industry, but not all shots are created equal in terms of how they work.

A study published in Nature investigated how genes affect the success of modern weight-loss drugs — specifically, GLP-1s like semaglutide and tirzepatide.

In analyzing genetic data and self-reported weight loss from over 27,000 users, researchers pinpointed a specific variation in the GLP-1 receptor gene (GLP1R) that acts as a “booster” for the drug’s effectiveness.

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Individuals carrying one copy of this variant lost an average of 1.6 pounds more than those without it, according to the findings.

This suggests that genetic testing could eventually help doctors steer sensitive patients toward medications they are more likely to tolerate.

“We believe these reports are a step forward in meeting an unmet need for a more informed and personalized approach to weight management,” said study co-author Noura Abul-Husn, chief medical officer at the 23andMe Research Institute in California, in a press release.

While this genetic “boost” is measurable, it remains relatively modest when compared to the total average weight loss of 24 pounds observed across the study population, the researchers noted.

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Beyond genetics, other factors such as age, sex and specific medications remain much stronger predictors of success.

For instance, the study found that women generally saw a higher body mass index (BMI) reduction (12.2%) compared to men (10.0%).

The study may also reveal why certain patients experience stomach issues. Scientists identified a different genetic variant that was linked to increased reports of nausea and vomiting.

The presence of this side effect did not impact the drug’s effectiveness, however. Patients with variants in the GLP1R and GIPR genes lost just as much weight as those without it; they simply felt more sick during the process, the study found.

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“GLP-1 treatment decisions are complex, and having access to clinical expertise to help contextualize your genetic results alongside your full health picture is exactly the kind of guidance this report is designed to support,” said Abul-Husn.

Dr. Peter Balazs, MD, a hormone and weight-loss specialist serving the New York and New Jersey area, was not involved in the study but reiterated the role of the genetic variants in treatment response and side effects.

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“Notably, there appears to be a drug-specific effect: The GIPR variant associated with these side effects is observed with tirzepatide, but not with semaglutide,” he told Fox News Digital.

Balazs said he was surprised by the extremely wide nausea risk range (5%–78%). “Additionally, the drug-specific genetic dissociation was unexpected,” he added.

Study limitations

The data relied on participants reporting their own weight, which could be subject to bias.

“The data is self-reported and not medically verified, which may affect its reliability firstly,” Balazs told Fox News Digital. “It also does not account for key treatment variables, such as titration, discontinuation or dosing schedules.”

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The 23andMe participant pool may not reflect a diverse, real-world population, he added.

“The study also lacks data on important clinical endpoints, such as diabetes progression, and severe adverse effects, such as gastroparesis or pancreatitis,” Balazs pointed out. “Many of its findings also have not been supported by more clinically and statistically robust studies.”

For example, a sub-study comparing these reports to objective iPhone health data suggested that participants might over-report their progress. While users reported an 11.8% loss, electronic data in that subset showed a 5.8% loss.

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As an observational study rather than a controlled clinical trial, it could not definitively prove that the genetic variants caused the difference in weight loss, only that they are associated with it, the researchers noted.

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“I think this article is interesting, raising the possibility of genetic factors, and the use of genetic testing incorporated into further decision-making when picking weight-loss medications,” Balazs said. “However, I would be careful to draw conclusions solely based on this study.”

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While U.S. cancer deaths have been falling over the past couple of decades, certain parts of the country are seeing less improvement in those numbers.

New research published in the British Journal of Cancer assessed the differences in cancer mortality improvements across the country.

Researchers at Mississippi State’s Social Science Research Center, along with scientists at Oak Ridge National Laboratory, analyzed death certificates between 1981 and 2019 across nearly 3,000 U.S. counties.

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The data was drawn from Wide-Ranging Online Data for Epidemiologic Research (WONDER), which is operated by the CDC. More than 21.3 million cancer deaths were included in the records.

Overall, U.S. cancer mortality has declined by about 32% between 1991 and 2019, but not all areas experienced that level of improvement.

The highest rates of mortality decline and the biggest drop in excess deaths were seen in urban, coastal and higher-income counties, according to the study. Rural and lower-income counties had smaller declines in mortality.

“In a complex nation such as the U.S., we should not be too surprised that there are large differences in health outcomes shaped by the diversity and variety of local regions and groups,” Arthur G. Cosby, the study’s lead author, told Fox News Digital. He is a Giles Distinguished Professor Emeritus at Mississippi State. 

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“Cancer improvement over the last few decades certainly aligns with this perspective,” he said. 

The gap appeared to widen over time, researchers noted. By 2019, the top 10% highest-income counties had a roughly seven times greater mortality improvement than the lowest-income counties.

The large urban centers along both the Atlantic and Pacific coasts consistently had among the highest rates of cancer improvement, according to Cosby. Rural and smaller cities in the interior of the U.S. often had much lower rates.

“The magnitude of the mortality differences between coastal and inland regions, [and] the large differences between places with different income levels and rural/urban places, were larger than I anticipated,” Cosby said.

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“The link between improving health and increasing disparities is poorly understood. I am pursuing that question now,” he added.

The researchers pointed to several factors that could contribute to the declines in cancer mortality. These included a decline in tobacco use and improved cancer screenings and treatments.

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“Wealthy, metropolitan New York City has been aggressive in instituting tobacco control measures, and the results show,” Cosby noted. “Manhattan had a lung cancer rate of 49 per 100,000 in 1991. By 2019, it cut its rate to 19.6 — a 60% reduction.”

Dr. Marc Siegel, Fox News senior medical analyst, agreed that more aggressive preventive measures targeting smoking and alcohol use likely played a role in the sharper mortality decline in urban, affluent areas.

“More aggressive screening campaigns, including at major medical centers, can diagnose pre-cancers or cancers earlier,” Siegel, who was not involved in the study, told Fox News Digital.

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A focus on improved lifestyle habits and less exposure to environmental toxins could also play a role, he added.

The study had some limitations, as noted by the authors.

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Because the research was conducted at the county level, the results may not apply at the individual level. 

Also, unmeasured factors such as lifestyle behaviors and access to healthcare could impact mortality.

“There are many limitations associated with the use of death certificates in research, such as accuracy of cause of death, possible multiple causes and changes in medical explanation for death over time,” Cosby told Fox News Digital.

Based on the findings, the researchers are calling for more studies that take into account the significant variations that exist across the country.

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“The varying speed of adoption of life-saving interventions between geographic places may produce increasing disparities,” Cosby said. “It is possible to have a situation where nearly all places are improving their cancer mortality, but at much different rates.”