A new low-calorie diet AF trial in JAMA shows older patients with persistent atrial fibrillation can drop real weight and keep it off for years. But the trial also shows that weight loss alone may not ease AF symptom severity, even at 3.5 years.

The open-label randomised clinical trial ran at two UK hospitals. Matteo Sclafani, MD, of John Radcliffe Hospital in Oxford, led the work, published online in JAMA on 20 May 2026. The trial recruited 118 adults aged 60 to 85 with persistent AF and a body mass index (BMI) of 27 or higher.

How the low-calorie diet AF trial was run

Patients were referred for cardioversion between November 2018 and April 2025. The team randomly assigned them in a 1:1 split.

The intervention arm (n = 59, mean age 68.5 years, 66% male) followed an 8-month low-calorie diet with regular behavioural support. The usual care arm (n = 59, mean age 68.3 years, 68% male) received a single face-to-face nurse consultation and written diet advice.

The primary outcome was a drop in AF symptom severity. Researchers measured this using a subscale of the AF severity scale, which is scored from 0 to 35. Higher scores reflected greater symptom load. Secondary outcomes included AF burden, body weight, and physical performance.

The team ran primary and secondary checks at 8 months. An interim review came about 4 months. An exploratory analysis tracked long-term weight and symptoms over a mean of 3.5 years.

Weight loss was clear at 8 months

At 8 months, the low-calorie diet AF trial intervention group lost 6.9 kg more than the usual care group. That worked out to a 9.7% body weight drop versus 3.1% in usual care (P < .001).

That figure puts the intervention well above the 5% threshold often cited for clinically meaningful weight loss.

AF symptoms did not budge

In the low-calorie diet AF trial, severity scores for AF symptoms did not differ between groups at 4 or 8 months. The pattern held across the secondary outcomes too.

• AF burden: no significant difference.
• Freedom from AF: no significant difference.
• Physical performance: no significant difference.
• Cardiac MRI measures: no significant difference.
• Health-related quality of life: no significant difference.
• Blood pressure and lipid levels: no significant difference.

The intervention was safe and well tolerated. No serious adverse events tied to it were logged.

Long-term weight loss but no symptom payoff

At 3.5 years, the low-calorie diet AF trial intervention group still weighed significantly less than usual care patients (P < .001). The estimated difference was 4.9 kg.

But the long-term low-calorie diet AF symptom story stayed the same. Severity scores did not differ between groups long-term either.

That gap between weight outcome and symptom outcome is the headline of the trial.

What the editorial said

The findings will land with mixed reactions in clinical cardiology. The accompanying editorial pushed against a passive read of the data.

"Rather than taking findings from the current study as supporting inaction with respect to weight loss, these current data, alongside prior evidence, may spur on a sense of urgency to help patients with healthy lifestyle choices as soon as an atrial fibrillation diagnosis is made," wrote Gregory M. Marcus, MD, MAS.

The editorial's read: intervention timing may matter. Diet support right after diagnosis, rather than years later, could yet produce symptom gains.

The investigators flagged a few caveats. The trial was open-label, which can bias subjective patient-reported outcomes like symptom scores.

Some assessments could not be completed for all participants because of the COVID pandemic. The weight loss in the intervention arm was moderate. The authors noted it was likely too small to drive substantial gains in blood pressure, lipid levels, or C-reactive protein.

What clinical teams should take from the low-calorie diet AF trial

For cardiology teams, the trial offers two clear takeaways. First, dietary weight loss works and lasts in this older AF group. Second, weight loss alone does not improve symptom scores in this specific subgroup.

That nuance matters for patient counseling. Clinicians can recommend dietary weight loss for its general cardiometabolic gains. But they should not promise symptom relief from weight loss alone.

Coverage on Medigear.uk shows why cardiology and electrophysiology teams must track how the low-calorie diet AF trial findings shape weight-management advice in AF care.

Source: Originating coverage based on Medscape reporting on the JAMA paper led by Matteo Sclafani, MD, John Radcliffe Hospital, Oxford, England. Published online 20 May 2026. Accompanying editorial by Gregory M. Marcus, MD, MAS. Funding from the University of Oxford, the National Institute for Health and Care Research Oxford Biomedical Research Centre, the British Heart Foundation, and the DigiCardiopaTh PhD program.