Tell me please if have to include the definite article before the word chance in the following sentence.
If you lose weight too quickly, then (the) chances are you are going to gain the weight back very soon.
If I need to include it, then tell me why please.
In a formal context, you would write "the chances are that you are going to gain the weight back". Articles and conjunctions are often omitted in informal speech and writing, especially with set phrases such as "[the] chances are [that]" something will happen, is the case, etc..
