I can think of so many reasons. But for me, Diet Coke and low fat are the two main culprits. It was fine when I was young because I'd burn it off and I just didn't eat enough to ever let myself get fat. But once I added in the sleep deprivation from babies, I literally needed a Diet Coke to get out of bed in the morning. Little did I know that Diet Coke and carbs were making me hungry. And so I snacked on more Diet Coke and carbs and that made me even more hungry. It's so obvious to me now, I don't know why I couldn't see it before.