Museli is a healthy food, but you need to be wary of portion sizes as it can be high calorie due to the nuts and dried fruit. Nuts also add too the fat content.
Be aware that low fat does not mean low calorie - eg low fat yogurts simply replace the fat with sugar, resulting in a similar calorie content only without the satiety factor of the normal yogurt.
Wholegrain carbs, fruit, veg, beans pulses and lentils are all filling low fat food, but as with all things moderation is key.