Energy balance

In free-living sedentary adults consuming ad libitum, increasing dietary fat percentage (>35% energy) promotes weight gain primarily by increasing total energy intake, whereas low-fat diets (<25% energy) support weight maintenance by limiting total energy intake.

If you are trying to prevent weight gain without strict calorie counting, focusing on a lower-fat diet (under 25% of calories from fat) may help you naturally consume fewer calories. In this study, people eating higher-fat diets ate more total food and gained weight, while those on low-fat diets maintained their weight. The key is that lower fat helped control total energy intake, not that fat is inherently bad.