María asked when we include "do" or "does" in a comparison. "I have a question about the following sentences: 'She eats more healthy food than I do.' and 'She has fewer video games than Stephen.' Why do we end the first sentence with 'than I do`' but do not end the second sentence with 'than Stephen does?' Why is there no 'does' after 'Stephen?' What is the difference between the sentences?
The "do" or "does" in the second part of a comparative is optional. You can say "She eats more healthy food than I do" or "...more healthy food than I." Many native-speakers of U.S. English INCORRECTLY would say "She has more healthy food than me." So many people commit this error that people who care about grammar are almost embarrassed to say "She has more healthy food than I" for fear of sounding pretentious. For this reason, they (and I) tend to say "...than I do" instead of "...than I." The following all are correct: She eats more healthy food than I do. She eats more healthy food than I. She has fewer video games than Stephen does. She has fewer video games than Stephen. Again, the use of "do" or does" in these cases is optional. I recommend adding "do" after than I, than you, than we, or than they, and "does" after than he, she, or it. Whether you add "does" after than Stephen, than David, or than Joelia, however, is entirely up to you. Thank you again for an excellent question. Have a great evening!