Someone sad that less food leads to weight gain

I eat less then before but nothing is happening. I was 76kg and after three weeks I am 76kg. Someone said that less food leads to weight gain? How is that possible? What am I doing wrong?

Even when people eat less high-fat food, they still can gain weight from eating too much of foods high in starch, sugars, or protein. You should eat a variety of foods, emphasizing pasta, rice, bread, and other whole-grain foods as well as fruits and vegetables. And these foods are filling, but lower in calories than foods rich in fats or oils. However, the pattern of eating may also be important. Snacks provide a large percentage of daily calories, unless nutritious, snacks are part of the daily meal plan, snacking may lead to weight gain.