Knowing which works better is critical for employers' health plans, because anti-obesity drugs now account for about 17% of U.S. employer health plan prescription spending, according to CBIZ.

Related: 5 worst states for obesity

The full retail price of the drugs is about $1,400 per month for Victoza; $1,500 per month for Wegovy, a better-known drug that's similar to Victoza; and just $200 per month for Qsymia.

Knowing which patients have the genes that make them good candidates for which anti-obesity drugs could help employers hold down their health plans' prescription drug benefits costs while maximizing the amount of help the plan participants get with controlling their weight and avoiding costly conditions such as heart attacks.

The Cifuentes team's study appeared last week in Cell Metabolism, a peer-reviewed research journal for scientists with an interest in cell biology, cell metabolism and endocrinology.

Phenomix: Phenomix is a company that hopes to use gene sequencing technology to improve care for people with obesity.

The Mayo Clinic and two of the Mayo Clinic researchers on the list of study authors have licensed some of their obesity research to Phenomix.

Study details: The researchers based their study on an analysis of a group of about 717 adults who had a body mass index over 30.

An individual's body mass index is equal to the individual's mass in kilograms divided by the square of the individual's height in meters.

Human beings have about 6.2 billion "nucleotides," or pairs of the nucleic acids adenine, cytosine, guanine and thymine, in their "DNA," or threads of genetic information that human cells use to reproduce.

The researchers tested the subjects' DNA for "single nucleotide polymorphisms," or differences from the most common nucleic acid sequence, that might be associated with obesity.

The researchers also tested the participants' blood sugar levels, hormone levels and other indicators, such as how much participants had to eat at a meal to feel "satiated," or full.

The researchers used the traditional, non-genetic tests to classify the patients as Hungry Brain patients, who become obese because their brains tell them to eat more, and Hungry Gut patients, who become obese because their stomachs tell them to eat more.

The Hungry Brain patients responded better than Hungry Gut patients to a version of Qsymia: At 52 weeks, they'd lost an average of 17% of their body weight. Hungry Gut patients who took a combination of phentermine and topiramate lost just 11% of their body weight.

The researchers measured patients who'd taken liraglutide, a GLP-1 agonist similar to semaglutide and tirzepatide, after 16 weeks. For liraglutide users, the average weight loss was just 3.3% for Hungry Brain patients but 6.4% for Hungry Gut patients.

The SNP tests showed that some gene differences correlated with whether the patients had a Hungry Brain or Hungry Gut type, but the pattern was more complicated that what the researchers had expected.

Overall, the research supports the idea that GLP-1 agonists may work better on patients who fill up relatively easily but then get hungry anyway, according to the researchers.

Phentermine-topiramate combinations may work better on people who have to eat a great deal to feel full.

The future: The researchers note that they started with a non-random sample of patients and that relatively few of the patients were male or had diabetes.

The researchers want to conduct more research designed in such a way that they can analyze the impact of gender, dietary patterns, health status, socioeconomic status and other variables.