Clinical Context
The relationship between obesity and cardiovascular disease has long been recognized, but proving that weight loss reduces cardiovascular events has proven challenging. Previous weight loss interventions—whether through lifestyle modification, bariatric surgery, or medications—have struggled to demonstrate reduced cardiovascular mortality in randomized trials. This evidentiary gap led some to question whether obesity itself causes cardiovascular events or merely travels alongside other risk factors.
The SELECT trial (Semaglutide Effects on Cardiovascular Outcomes in People with Overweight or Obesity) fundamentally changed this landscape. It was the first dedicated cardiovascular outcomes trial of an anti-obesity medication in patients without diabetes, and it demonstrated a 20% reduction in major adverse cardiovascular events (MACE) with semaglutide 2.4 mg weekly. This weight loss analysis from SELECT provides crucial data on the magnitude and durability of weight reduction achieved over 4 years—far longer than typical obesity medication trials.
Understanding these long-term weight trajectories is essential for clinicians counseling patients about realistic expectations with semaglutide therapy and for understanding how sustained weight loss relates to cardiovascular protection.
Study Summary (PICO Framework)
Summary:
In adults with preexisting cardiovascular disease, overweight or obesity, and no diabetes, semaglutide 2.4 mg weekly for up to 208 weeks significantly reduced body weight by 10.2% compared to 1.5% with placebo, with substantial reductions in waist circumference (-7.7 cm) and waist-to-height ratio, though discontinuation rates were higher in the semaglutide group, particularly among those with lower baseline BMI.
| PICO | Description |
|---|---|
| Population | Adults aged ≥45 years with BMI ≥27 kg/m², established cardiovascular disease (prior MI, stroke, or symptomatic PAD), and no diabetes. N=17,604. |
| Intervention | Semaglutide 2.4 mg subcutaneously once weekly (titrated over 16 weeks) for up to 208 weeks (4 years). |
| Comparison | Matching placebo administered weekly with standard cardiovascular care. |
| Outcome | Mean weight loss of 10.2% with semaglutide vs 1.5% with placebo. Waist circumference decreased by 7.7 cm. Weight loss was sustained through 4 years of treatment. Serious adverse events were fewer with semaglutide despite higher discontinuation rates. |
Clinical Pearls
1. Weight loss of ~10% is sustained over 4 years. Unlike many weight loss interventions where weight regain begins within 6-12 months, semaglutide maintained approximately 10% weight reduction throughout the 208-week follow-up. This durability is remarkable and supports long-term therapy for sustained benefit. The plateau occurs around week 65, after which weight remains stable.
2. Visceral fat reduction may drive cardiovascular benefit. The 7.7 cm reduction in waist circumference suggests substantial loss of visceral adipose tissue, which is more metabolically active and inflammatory than subcutaneous fat. Visceral fat reduction improves insulin sensitivity, reduces inflammatory cytokines, and decreases atherogenic lipoproteins—all mechanisms potentially contributing to the 20% MACE reduction observed in SELECT.
3. The 2.4 mg dose is critical for these results. SELECT used semaglutide 2.4 mg (the obesity dose), not the 1.0 mg dose approved for diabetes. Clinicians prescribing semaglutide for cardiovascular risk reduction should target the higher dose to replicate SELECT’s benefits. Undertitration may compromise both weight loss and cardiovascular protection.
4. Patients with lower BMI had higher discontinuation rates. This counterintuitive finding may reflect that patients with less obesity reach uncomfortable levels of weight loss more quickly, or experience proportionally greater side effects. Clinicians may need to consider dose reduction or treatment holidays in patients approaching normal weight.
Practical Application
Patient selection for cardiovascular risk reduction: Based on SELECT, consider semaglutide 2.4 mg for patients with established cardiovascular disease (prior MI, stroke, or peripheral arterial disease) and BMI ≥27 kg/m², regardless of diabetes status. These patients have a favorable risk-benefit profile with a number needed to treat (NNT) of approximately 67 over 3 years to prevent one MACE event.
Setting expectations: Counsel patients that maximum weight loss occurs around 12-15 months, with approximately 10% reduction expected. Initial weight loss is rapid (4-5% by 6 months), then slows. Weight loss is sustained with continued treatment but will reverse if medication is stopped. The primary goal is cardiovascular protection, with weight loss as an important mechanism.
Managing the weight plateau: When patients reach their weight plateau (typically at 10-15% loss), reassure them that this stabilization is expected and beneficial. Continued treatment maintains the cardiovascular protection. Resist the urge to discontinue therapy just because weight loss has stopped.
Monitoring: Beyond weight, track waist circumference as a marker of visceral fat reduction. Monitor for gastrointestinal side effects, which are the main cause of discontinuation. Consider periodic assessment of cardiovascular risk factors (blood pressure, lipids) which typically improve with weight loss.
How This Study Fits Into the Broader Evidence
SELECT is the first obesity medication trial to demonstrate reduced cardiovascular mortality. Previous trials of anti-obesity drugs (SCOUT with sibutramine, LIGHT with lorcaserin) either showed harm or were neutral for cardiovascular outcomes. SELECT’s positive results have transformed how we view obesity treatment—from a cosmetic concern to a cardiovascular intervention.
The weight loss observed in SELECT (~10%) is less than in the STEP trials (~15-17%), likely reflecting the older population with more comorbidities and the cardiovascular disease burden. Nonetheless, even this more modest weight loss translated into significant cardiovascular benefit.
Current guidelines from the ACC/AHA now recognize semaglutide as a treatment option for cardiovascular risk reduction in patients with obesity and established cardiovascular disease, independent of diabetes status. This represents a paradigm shift in obesity management.
Limitations to Consider
SELECT enrolled patients with established cardiovascular disease; extrapolation to primary prevention is uncertain. The trial population was predominantly White and male, limiting generalizability. Long-term effects beyond 4 years, including potential for weight regain if therapy is discontinued, remain unknown. Cost and access barriers may limit real-world implementation.
Bottom Line
Semaglutide 2.4 mg produces sustained weight loss of approximately 10% over 4 years in patients with obesity and established cardiovascular disease. This weight reduction, particularly the loss of visceral fat reflected in waist circumference changes, likely contributes to the 20% reduction in cardiovascular events observed in SELECT. For patients with obesity and cardiovascular disease, semaglutide represents a evidence-based intervention for both weight management and cardiovascular risk reduction.
Source: Ryan, Donna H., et al. “Long-term weight loss effects of semaglutide in obesity without diabetes in the SELECT trial.” Nature Medicine, 2024 Jul. Read article here.
