Diet versions of foods (low-fat yoghurt, sugar-free desserts, reduced-fat crisps) typically replace fat or sugar with additives. The result is less satisfying, often more processed, and frequently consumed in larger volumes.
What works instead
Full-fat Greek yoghurt with fruit instead of low-fat fruit yoghurt. Real butter in small amounts instead of margarine. Real chocolate in small portions instead of diet versions. Better food in smaller amounts.
Most users find they eat less when they're not eating 'okay' diet versions. The full-fat options provide satiety the diet versions don't.