There is no diet on earth that works so that once you do it, you are 'fixed.'
Absolutely none. Even bariatric surgery has the effect that 'life goes on' and you have to adjust everything you eat to the aftermath. There is no magic fix. Atkins tells you to eat a certain way and you must always do that. When you don't, you've 'fallen off the wagon' - hence, the Atkins maintenance diet which you must observe and obey the restrictions or go back to even stricter induction.
Weight Watchers is completely upfront about how you must always watch what you eat. Lifelong members, rewarded for reaching goal, get to weigh in once a month so that they can jump back into the program if they go 5 pounds over their goal weight.
More insidious than the presence of sugar is the presence of fat. 'Cut fat out of your diet' and log the food you eat in fitday. You'll still see that fat is a part of the food you eat. It carries flavor, making the food you eat taste good. But why even compare sugar and fat? Sugar is a carbohydrate. You'll see that a gram of sugar has 4 calories, the same number as protein. You'll probably taste sugar sooner than you'll taste fat.
Fat has more than twice the number of calories as sugar. 9 calories in the same unit, one gram. Are you necessarily going to 'taste the fat'? No. Look at an egg - do you taste the fat in a boiled egg? You end up thinking that low-fat is not frying an egg. The fat is there anyway, hello, and you're not even thinking about it... and it's got a bonus of being highest in calories.
This is why low-fat diets work. They may be so 'yesterday' in terms of popularity but the are based on fat's caloric punch. Go on a 'low-sugar' diet, just looking at sugar and you'll make some progress in calorie control, but fat is going to be an ever-present consideration.