GLP-1 and Heart Health: What the SELECT Trial Means for You

Why Cardiologists Are Now Prescribing GLP-1 Drugs

The SELECT trial results, published in the New England Journal of Medicine in late 2023, fundamentally changed how cardiologists think about obesity treatment. Semaglutide wasn't just a weight loss drug — it was now a cardioprotective drug. The distinction matters enormously.

What SELECT Actually Showed

SELECT enrolled 17,604 patients who met two criteria: (1) BMI ≥27 (overweight or obese) and (2) established cardiovascular disease — prior heart attack, stroke, or peripheral arterial disease. Crucially, none of them had type 2 diabetes. This was a clean test of semaglutide's cardiovascular effects in non-diabetic patients with obesity and high CV risk.

At an average follow-up of 39 months: - 20% relative reduction in major adverse cardiovascular events (MACE): The primary composite endpoint of cardiovascular death, non-fatal heart attack, or non-fatal stroke - This reduction was consistent across all three components of MACE - Absolute risk reduction of 1.5% over 3+ years — translating to a number needed to treat of ~67 patients to prevent one event - Benefits appeared within the first year and continued to accumulate

For context: a 20% MACE reduction is comparable to what's seen with statins in high-risk populations. Adding a GLP-1 drug on top of standard-of-care treatment (most patients were already on statins, aspirin, and ACE inhibitors/ARBs) produced incremental benefit of this magnitude.

Why This Matters for Non-Diabetics

Prior to SELECT, the cardiovascular outcome trials for GLP-1 drugs (LEADER for liraglutide, SUSTAIN-6 for semaglutide, REWIND for dulaglutide) were conducted primarily in people with type 2 diabetes. Cardiologists and patients without diabetes had to extrapolate.

SELECT removed this uncertainty. The cardiovascular benefit of semaglutide exists independently of glucose-lowering effects — because these patients weren't hyperglycemic to begin with. The benefit comes from:

1. Weight loss: An average of 9.4% body weight reduction over the study
2. Direct vascular effects: GLP-1 receptors are expressed in cardiac and vascular tissue; there appear to be anti-inflammatory and anti-atherogenic effects beyond weight loss
3. Blood pressure reduction: Modest but consistent (~3 mmHg systolic)
4. Lipid improvements: Triglycerides reduced, HDL modestly increased

Post-hoc analyses are ongoing to separate how much of the benefit is mediated by weight loss vs. direct pleiotropic effects. Early evidence suggests both contribute meaningfully.

How the SELECT Trial Changes Prescribing

Expanded indication: Following SELECT, semaglutide (Wegovy) received FDA approval for reducing major cardiovascular events in adults with obesity and established cardiovascular disease. This is the first anti-obesity medication to receive a cardiovascular indication.

Insurance coverage: Many major insurers are now covering semaglutide for patients with obesity and CVD, citing the SELECT data — even for patients who might previously have been denied.

Cardiology guidelines: The American Heart Association and American College of Cardiology have updated guidance to include GLP-1 agonists in the treatment algorithm for high-risk cardiovascular patients with obesity.

What This Means for Patients Without Cardiovascular Disease

If you're using semaglutide for weight loss but don't have established CVD, the SELECT trial's direct applicability is limited — those were specifically very high-risk patients.

However: - The mechanism by which semaglutide reduces cardiovascular events (weight loss + direct vascular effects) operates in lower-risk patients too - Metabolic syndrome and obesity are themselves major risk factors for CVD — treating them has long-term cardioprotective value - Later trials in primary prevention (reducing risk before a first event) may show similar patterns

For now: the SELECT data reinforces that semaglutide is doing more than just lowering body weight. You're not just losing weight — you're reducing systemic inflammation, improving vascular function, and lowering the metabolic load on your cardiovascular system.

Semaglutide vs. Tirzepatide: Does Tirzepatide Have the Same CV Benefit?

The SURMOUNT-MMO trial — the cardiovascular outcome trial for tirzepatide in non-diabetic patients with obesity — is underway with results expected in the next few years. The SURPASS-CVOT trial in diabetic patients is also ongoing.

Given the mechanistic overlap (tirzepatide activates GLP-1 receptors plus GIP receptors, and produces even greater weight loss than semaglutide), most cardiologists expect tirzepatide will show comparable or superior cardiovascular benefit. But the SELECT-equivalent trial data doesn't exist yet for tirzepatide.

For patients specifically seeking a GLP-1 drug for cardiovascular risk reduction alongside weight loss, semaglutide currently has the stronger data package. For patients prioritizing maximum weight loss, tirzepatide's efficacy is consistently higher.

The Bottom Line

SELECT demonstrated that semaglutide is a cardiovascular drug, not just a weight loss drug. A 20% reduction in heart attacks, strokes, and cardiovascular death in high-risk patients without diabetes changes how we should think about the risk-benefit calculus of GLP-1 therapy.

If you have obesity and cardiovascular disease — or metabolic syndrome with multiple risk factors — the conversation with your physician should explicitly include the SELECT data. At Marrow, we review your full cardiovascular risk profile at intake and help you understand what the evidence shows for your specific situation.