If a new study is to be believed people with a higher body mass index (BMI) have a significantly higher risk of developing atrial fibrillation than those with a normal weight. Atrial fibrillation is a condition that makes your heart race faster that could put you at a risk of stroke. People with a higher BMI are said to be prone to get affected by atrial fibrillation and this could be reduced if you exercise. People who reported that they didn't exercise at all had about double the risk of developing fibrillation when compared to those who were physically active