What grammatical issue is present in: "Although my friend and I both followed the same exercise program, she lost more weight than me."?

The sentence "Although my friend and I both followed the same exercise program, she lost more weight than me" contains a grammatical issue related to the misuse of pronouns. In this context, the correct pronoun to use is "I" instead of "me."

When a comparison is made between two subjects, the pronoun should be in the subject form. In this case, "she lost more weight than I [did]" is the appropriate construction, as "I" is the subject pronoun. The phrase can be understood as being implied: "than I lost." This grammatical nuance highlights the importance of using proper pronoun forms to maintain clarity and correctness in writing.

In contrast, the other choices do not apply to this sentence. The sentence does not suffer from excessive commas, inconsistencies in verb tense, or lack any errors overall. The focus remains on ensuring that pronoun usage follows the grammatical rules dictated by the structure of the sentence.