There seems to be a debate between various types of diets. On the one hand there is the low fat diet that encourages eating a diet lower in fats and overall percentage of calories coming from fats. There are also the low carb diets that are designed for people to stay away from carbohydrates to lose weight. Either of these actually does cause people to lose weight. Which one is best for long term weight loss?
What happens in most cases is that the people who eat low carbohydrates typically lose more weight at first versus those who eat a diet lower in fats. While the reasons at times don't seem clear, it probably has to do with the discipline that it takes to eat this type of food.
There are so many things made with carbohydrates that a more disciplined dieter is needed to have success with a low carb diet. Much of the time, what most people consider to be comfort foods have to be completely avoided. This extra discipline probably explains why these type of dieters have more short term success than those eating low fat diets.
In the long run though, most people who lost weight by avoiding carbohydrates eventually start eating the diet they were used to before losing weight. Adding these back into the diet causes many to gain back much of the weight that was lost.
Avoiding fats, while not easy, is something that can be done easier over the long run. Changing from certain products like fatty meats to lean meats, low fat versions of products, and other changes are something that is easier to do after losing the weight. While there are those who can gain it all back, it's a much simpler plan to stick with in the long run as long as the changes that were put into place stay. Trying to do this lifelong avoiding carbohydrates is much more challenging.