This is how I explain it to my clients. I tell them straight up that if they're not losing weight they're eating too much. There's not another possibility. Fat is made of the food you eat and if you're gaining weight or maintaining weight when you're trying to lose weight them you're eating too much, period.  I hear way too often people talking about "I'm not losing weight because I'm not eating enough..." and I ask them how they think starving to death works and if they've ever seen pictures from Soviet or Nazi labor camps.