“I have to lose THE weight”.
“The” is used in English to differentiate between information that is known and information that is not known to the reader. If I said, “THE town”, I’d assume you’d know which town I was talking about. The location of “A town” is far more ambiguous.
Saying, “THE weight” implies that the reader should know that: a) the weight I mean is over what is ‘normal’, and b) it can be assumed to be bad. We don’t know that either of these things is true.
Stop throwing around your “the’s” all willy-nilly like you’re spending pennies in the arcades. Especially if claim to align yourself with body-positivity. Words have an impact, even if you don’t mean them to.