[hnuser1234]

If you are a 300 pound person and want to be a 150 pound person, you have to eat like a 150 pound person. Forever.

[ramblerman]

You are both correct, not sure why OP is downvoted though.

If your caloric requirements are 2400 calories a day. You might eat at a deficit for your diet, say 1700. And after that you can eat 2400 again.

[hnuser1234]

As body mass increases, the caloric intake required to maintain said mass increases. Likewise, as body mass decreases the caloric intake required to maintain said mass decreases. Fat people need to eat like the not-fat version of themselves in order to both lose weight and maintain their new mass. If "balance" is 2400 calories for their fat body, resuming eating 2400 calories will lead to them becoming fat again.