Atrial fibrillation has been called the new epidemic of the 21st century, with approximately 33.5 million patients worldwide afflicted by AF and the number of sufferers is growing. Overweight and associated cardiovascular and metabolic co-morbidities such as hypertension, diabetes, and sleep apnea syndrome are important causes of the atrial fibrillation epidemic. Studies have confirmed that overweight is associated with the development of AF, and since the role of overweight and obesity in AF is so important, and there are few overweight and obese patients with AF, can this group of patients benefit from weight loss as an intervention? Happily, weight loss as a lifestyle intervention can indeed reduce the AF load in patients with AF. Recent research in 2015 showed that gradual weight loss in overweight and obese patients with atrial fibrillation resulted in long-term improvements in atrial fibrillation burden, with a significantly lower risk of long-term maintenance of atrial fibrillation recurrence (by a factor of 6), and that weight fluctuations (>5%) were a risk factor for atrial fibrillation recurrence (by a factor of 2). (2-fold increased risk). This benefit is due to the fact that weight loss reduces or eliminates other concomitant cardiovascular risk factors (including impaired glucose tolerance, dyslipidemia, hypertension, and sleep apnea), and therefore, obese patients with AF can benefit greatly from weight loss as a lifestyle intervention. Lack of physical activity is one of the main causes of overweight and obesity. Increasing physical activity to improve cardiorespiratory fitness is also an important part of lifestyle change. Do patients with atrial fibrillation, especially those with obesity, need to increase physical activity? Is it necessary to increase physical activity to improve cardiopulmonary function in addition to weight loss? A study published in July 2015 in JACC, a leading cardiovascular journal, found that overweight patients with AF had a lower risk of AF recurrence if they had better cardiorespiratory fitness, and that improving cardiorespiratory fitness reduced AF recurrence, while improving cardiorespiratory fitness with weight loss led to better prevention of AF recurrence and reduced cardiovascular risk. It also reduces cardiovascular-metabolic disease risk factors, reduces inflammatory status and cardiac remodeling in patients. Therefore, in addition to scientific weight loss, obese and overweight patients with atrial fibrillation can benefit from scientific exercise to improve cardiorespiratory fitness. At a time when the incidence of both obesity and atrial fibrillation is increasing year by year, the importance of weight loss and physical activity cannot be overstated.