Nobody with a tendency toward overweight just wastes away to nothingness accidentally. You shouldn't worry about how to stop the weight loss once you reach your goal weight until you actually reach your goal weight. In other words, first find out if this will ever actually be a problem for you, otherwise, don't worry about it.
I think most people with a tendency toward overweight either never reach their goal weight (always have that last 5 or 10lbs to go) or else they do but they had to work very hard and so they know that the only way to maintain is to watch portions vigilantly indefinitely.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Highest squat: 167.5 x 2. Current Deadlift: 190 x 3