When you cook chicken in an air fryer, the high heat can cause the natural fats and oils within the meat to melt and render out. This process is common with all meats and does not necessarily mean that the dish will be lower in calories. Additionally, the circulating hot air in the air fryer can cause any surface oils or fats to be blown off the meat and collected in the bottom of the air fryer basket, which can contribute to the amount of oil you see after cooking.

If you air fry chicken without any added seasoning or marinade, it can help to reduce the overall calorie and fat content of the dish, as you are not adding any additional ingredients that may contribute to the calorie count. However, chicken legs do contain natural fats and calories, so even when cooking them plain in an air fryer, there will still be a certain amount of fat and calories present.

Using an air fryer to cook chicken legs without any added oil or seasonings can still be a healthier cooking method than deep-frying or pan-frying, which often requires a significant amount of oil to achieve a crispy texture. By air frying, you can achieve a crispy outer layer without the need for as much oil, which can help to reduce the overall calorie count of the dish.  It's important to note that not all fats are bad for you, and some types of fat can be beneficial to your health in moderation.

The key is to choose healthy fats, such as those found in nuts, seeds, avocados, and fatty fish, and to limit your intake of unhealthy fats, such as those found in processed foods, fried foods, and high-fat meats.