A low-calorie diet program helped older adults with overweight and persistent atrial fibrillation lose weight, but it did not improve their AFib symptoms or heart rhythm outcomes, according to a new clinical trial.
The study, published in JAMA, found that eight months of dietary weight loss and behavioral support led to significant weight loss without major safety concerns. However, that weight loss did not translate into fewer AFib symptoms, less time spent in AFib, improved heart structure or a reduced need for additional treatments to control heart rhythm.
Atrial fibrillation, often called AFib, is an irregular heart rhythm that can cause palpitations, fatigue, shortness of breath and dizziness. It can also increase the risk of stroke and other complications. Weight loss is often discussed as part of AFib care, especially because excess weight is linked with a higher risk of developing the condition.
But the new trial suggests the picture may be more complicated for older adults who already have persistent AFib.
The LOSE-AF trial included older adults with overweight and persistent atrial fibrillation. Participants were randomly assigned to either a low-calorie diet and behavioral support program or usual care. The goal was to test whether a structured weight-loss program could improve AFib-related symptoms and heart rhythm outcomes over eight months.
The weight-loss program did what it was designed to do. Patients in the intervention group lost significantly more weight than those receiving usual care, and researchers reported no safety concerns from the diet program.
But the main AFib outcomes did not improve. At eight months, the researchers found no meaningful difference in symptoms between the two groups. The program also did not reduce how much time participants spent in AFib, improve heart structure or lower the need for additional treatments to control heart rhythm.
The findings do not mean weight loss has no value for people with heart disease. Weight loss can affect many aspects of health, including blood pressure, blood sugar, mobility and overall cardiovascular risk. Instead, the study points to a narrower conclusion: in this group of older adults with persistent AFib, moderate weight loss over eight months was not enough to improve AFib-specific symptoms or rhythm measures.
That distinction matters because nutrition and weight-loss advice is often presented as if one change will improve every health outcome. In reality, the effects of weight loss may depend on a person’s age, the condition being treated, how long that condition has been present and what outcome researchers are measuring.
Persistent AFib may be harder to change through weight loss alone than earlier or less established forms of the condition. By the time AFib has become persistent, the heart may have undergone changes that make rhythm problems less responsive to diet and lifestyle changes alone.
The trial also helps separate two ideas that are often blended together: losing weight and improving a specific medical condition. In this case, the diet program helped participants lose weight safely, but that did not mean their AFib improved during the study period.
For patients, the findings are not a reason to dismiss nutrition or weight management. They are a reminder that heart rhythm conditions require individualized medical care, and that weight loss should not be viewed as a substitute for rhythm-control treatment, medications or other care recommended by a clinician.
For researchers, the study raises questions about whether diet and weight loss may be more effective for AFib prevention, earlier stages of AFib or different patient groups. It also suggests that older adults with persistent AFib may need more comprehensive treatment strategies than weight loss alone.
The LOSE-AF trial was led by University of Oxford investigators, and the university served as the trial sponsor. The study was funded by the National Institute for Health and Care Research Oxford Biomedical Research Centre, the British Heart Foundation and the DigiCardiopaTh PhD program.
Several authors reported funding, research support or professional roles outside this study, including support from the Wellcome Trust and the Royal Society, Slovak grant agencies, the European Union, Novo Nordisk, the Novo Nordisk Foundation and iRhythm. The iRhythm support involved electrocardiogram patch monitors for a separate atrial fibrillation screening trial.