Dr. Rekha Kumar on GLP-1s and the next wave of metabolic drugs

Dr. Rekha Kumar is an endocrinologist, obesity medicine specialist, and Associate Professor of Clinical Medicine at Weill Cornell Medicine. She is the Senior Medical Advisor at Found, a former medical director of the American Board of Obesity Medicine, and an Associate Editor of the journal Obesity. Her expertise spans the clinical treatment of obesity, metabolic syndrome, and the growing role of GLP-1 medications in long-term weight care.

In this Q&A, Kumar breaks down what researchers are discovering about GLP-1s beyond weight loss and what a new class of drugs could mean for the future of metabolic medicine.

The common misconception

What’s the biggest misconception your patients have about GLP-1s right now?

RK: I would say, that using medication for weight care is somehow cheating. This belief runs deep, among patients and among some clinicians too, because obesity has been so stubbornly framed as a willpower problem rather than a chronic metabolic condition. GLP-1s don’t work by bypassing effort. They work by correcting the underlying hormonal and physiological drivers of weight gain that lifestyle changes alone often can’t fully address.

The media hasn’t helped. Coverage tends to highlight dramatic transformations without explaining the physiology or the reality that long-term treatment is often necessary to maintain results. What we know from the evidence is clear: these medications treat obesity, and they deliver cardiovascular and metabolic benefits that extend well beyond the number on a scale. That’s not a shortcut. That’s the medicine doing its job.

Who GLP-1s are for

Who is actually a good candidate for GLP-1 treatment, and who isn’t?

RK: Strong candidates are adults with obesity or overweight with related health conditions like cardiovascular disease, type 2 diabetes, or hypertension, and those who haven’t achieved adequate results through lifestyle modification alone. Obesity is a chronic metabolic disease, and GLP-1s should be understood as one component of a comprehensive, personalized care plan that still includes nutrition, movement, and behavioral support.

Those who are generally not good candidates include people with certain gastrointestinal conditions, those who are pregnant or trying to conceive, and those seeking minor cosmetic changes rather than clinically meaningful metabolic improvement. Like any treatment, candidacy should be determined through a thorough clinical evaluation, which is exactly why personalized, clinician-led care matters so much in this space.

The access gap

GLP-1s are still inaccessible for most people who need them. If retatrutide gets approved, does it solve that problem, or does it start the access conversation all over again?

RK: Approval doesn’t automatically mean access, and we should be clear-eyed about that. In our current system, patients with more resources tend to have better access to specialists, newer therapies, and the clinical relationships needed to navigate treatment options thoroughly. Others face insurance barriers, limited local providers, or costs that simply put these medications out of reach.

Retatrutide’s approval, when it comes, will restart that conversation, not resolve it. What gives me hope is that telemedicine, transparent pricing, and access to licensed clinicians are removing many of the structural barriers that have historically made obesity care inequitable. The goal has always been the right medication for the right patient, and that has to be possible regardless of zip code or insurance status.

What the third receptor changes

Retatrutide is being called a “triple agonist” that targets GLP-1, GIP, and glucagon receptors. In plain terms, what does that third mechanism add, and why does it matter?

RK: Retatrutide works on three hormone receptors simultaneously: GLP-1 to reduce appetite, GIP to enhance insulin response and metabolic function, and glucagon to increase energy expenditure. That third mechanism, glucagon receptor activation, is what sets it apart.

While GLP-1 and GIP primarily work on the intake side of the equation by curbing hunger and improving blood sugar regulation, glucagon activation works on the output side, prompting the body to burn more calories and oxidize fat more efficiently. Think of it as addressing metabolic health from both ends at once. For patients who have plateaued on current medications or who have significant metabolic dysfunction beyond appetite alone, this dual-pronged approach could be clinically meaningful.

A meaningful clinical leap

Early trial data is showing significantly greater weight loss than current options. How do you interpret those numbers, and what makes retatrutide unique from other clinically effective obesity drugs?

RK: From a clinical standpoint, the early data are genuinely exciting, and I say that with appropriate scientific caution. We’re not just seeing greater weight loss percentages. We’re seeing meaningful improvements across the full cardiometabolic picture: better blood sugar control in people with type 2 diabetes, reductions in blood pressure, and signals of improvement in fatty liver disease.

What makes retatrutide distinct isn’t one number. It’s the breadth of effect. Current best-in-class options are already strong, but retatrutide’s triple mechanism appears to address more of the underlying metabolic dysregulation that drives obesity as a disease. If the Phase 3 data holds, this could represent a genuine step change in what we’re able to offer patients.

What the research shows so far

What does the current research show, and what are we still waiting to understand before retatrutide could be widely prescribed?

RK: Early-phase trials have shown impressive results: substantial weight loss, improved cardiometabolic markers, and mechanistic signals that suggest the triple agonist approach is working as intended. What we’re still waiting on is the full picture, specifically long-term safety data, durability of effects after extended use, and a clearer tolerability profile across diverse patient populations.

Phase 3 trials will be essential for understanding how retatrutide performs outside of controlled research settings, and in patients with the kinds of comorbidities we see every day in clinical practice. The promise is real; the science just needs to complete its process.

Since this interview, a second Phase 3 trial by drugmaker Eli Lilly has reported results, this time in people with type 2 diabetes. Participants on the highest dose lost an average of 36.6 pounds over 40 weeks, with meaningful improvements in blood sugar control. Six additional trials are expected to report this year.