Brother, i myself have been thin, i have become fat 94 kg in the past (without fitness..so way less muscles) (207 pounds), i have also become muscular in my life. As a person who has experienced all the types so to say with many different "diets", my conclusion? Diets do NOT work. Sub'han'Allah, the Islamic way of life is really the answer. I am NOT saying this because i am a Muslim.
I myself follow logic and rationality, the Islamic way of life, gives EXACTLY that. Be active, eat, but NEVER make your stomach full. 1/3 food, 1/3 water 1/3 air. Fast Mondays and Thursdays and also if possible ever 13th, 14th, 15th of each month you will see that you suddenly have MORE energy. When fasting i observed my body and strangely enough it almost feels like i had been working out. My muscles are more tight and i also have more energy. Logically thinking it could be that the body when eating, your food contains all kind of bacteria. When you do not eat, your body switches to cleaning it self as it is deprived of extra water and toxic stuff. When you are deprived of toxic stuff, everything becomes more healthier and because less water in the body, you can feel every muscle in your body if you for example would stretch your muscles.
Eat ONLY during certain times. So when fasting, during iftar..eat..(like the Islamic way of not filling it up), however what you eat also stay with 7 or 9 dates(I have concluded that dates are CRUCIAL). Drink some fluid and eat something that gives you energy for longer period (pasta, potatoes or rice) (again..moderate..the Islamic way). Eat SLOWLY. Chew more on the food as more nutritious will be used from it. After Isha..DON'T eat anymore. You can drink water, but NOT eat anything. Sleep after Isha prayer. If you would fast the next day, wake up before fajr..again eat some dates ( i myself try every day in the morning to eat 7 and during Maghreb 7). Because i eat dates every day, i do not need meat that much as dates already contain iron, as well as little amount of protein

. Protein is also found in almost anything. I eat meat when i want to these days and that is sometimes maybe once every 2 weeks or once a month. Strange thing is, i don't miss it even that much. Because my taste buds have gone to their original state, i taste things WAY better than before. I don't drink coke or any of those stuff. When i do eat meat, i even taste a lot of fat, which before i did not. The meat of the present day contains A LOT of fat. BTW, you have those people who say you NEED to eat meat, the argument against it, is simple. A silverback gorilla, what meat does he eat? It is a vegetarian =_=!. This whole issue with YOU NEED to eat meat is propaganda talk of those meat companies. Your body is amazing as it can get many nutritious stuff from almost everywhere. For example sugar is added to the body because of carbohydrates. Listen to the your body. When it craves for something, THEN go also eat that. For example every now and then (a month or so) my body is craving for meat. So i go and eat meat that day.
I am myself trying to slowly change also other habits of making own bread as many food that we eat isn't as they say it is. A lot of stuff have been added to it, that messes with the body. Many food for example contain E621. It adds flavous like salt does, but this also takes away your feeling of satisfaction. When you have eaten food that contains that, it feels like as if you have not eaten anything and you still feel as if you need to eat.
If you can't stop eating, this also has A LOT to do with having a weak will. People who don't have a very strong will, are often more fat. Fix yourself i would say and find the cause of this weak willed mentality.
Nobody is fat by default, their mind is fat. The body is just a reflection of the mind.