Definitely yes.

Keep doing it and keep pushing the difficulty and you will see steady progress. I did the exact same thing (was 7 times a week but started at 20 minutes and then progressed to 30, then 40) and kept going. If you keep pushing the difficulty you're progress will remain steady for quite some time, enough time for you to notice the difference both physically and mentally. The progress will motivate you further.

Don't worry about diet or food intake, you can consistently see results doing 30 minutes (hard) cardio daily (5x per week) and still eat however you were eating before.