Having a very low-fat diet helps because it generally translates into a lower-calorie diet.
Bumping up the amount of protein in your diet helps because the body burns much more calories in digesting protein than it does digesting carbohydrates or fats.
Eating a whole-foods, plant-based diet helps because the body requires a certain level of nutrition, and so if your diet is highly nutritious, the body will be satisfied with fewer calories.
All these are subtle strategies to facilitate losing weight.