You don’t have to eat everything that’s low in sugar but switching at least one normal bad habit is good way to begin. Meaning instead of the normal bag, just switch out for a protein shake.
The normal time you spend sitting at a desk for 1 hour doing lunch. Take a 1 hour walk or do a 15-30 min lunch then walk for 15-30 min. Start switching those weight gaining habits one by one for good habits and you’ll be on your way to losing those 15 pounds or fitting into those jeans or dress you want.