Short answer is...you don't.
Females usually lay 5-6 clutches a year. I had two last year that layed 11 clutches each. Once they start the only way I know of to stop them is to cool them down which will be almost impossible with summer coming. I suggest you feed them very well and toss the eggs if you don't want them or can't keep the babies.
There is no reason why they should be losing any significant amounts of weight if you are giving them enough food.
North Coast Geckos