Is it true that if you lose weight fast, you gain it faster and double the weight you lost?

luluu
i lost 40 kg in a month ,today is the last day in the month.I'm scared that I will gain the 40 kg back.So can I gain them back even if I ate a normal amount of food?
Is it true that if you lose weight fast, you gain it faster and double the weight you lost?
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