Is eating a low-carb diet (atkins or south beach) the only sufficient way of losing fat?

If you know, why are you asking others for advise? There are no shortcuts. You need to balance diet and exercise. Less calories and more exercise. I would never recommend a crazy diet, low carbs. Carbs are essential. Without them, you will get weak and binge eat. Your body will start to use muscle for energy and that is bad. It sounds to me like you are pretty knowledgeable so just use your common sense- everything in moderation. You only gained it all back because you were denying yourself good food. I have gotten in great shape, lost 30 lbs., lowered blood pressure, great blood tests (lipids, etc) and I look forward to eating. I have absolutely no desire to over eat. It really is more about forming great diet and exercise habits. Running for 2 hours every day is clearly overdoing it- come on, you know that. No wonder your body wanted FOOD! Just go easy, pick whole foods, yes, carbs, lots of proteins, good fats, etc. and exercise at least 30 minutes a day and you'll be fine. Give it time and be patient, Rome wasn't built in a day.