No matter how, it is always calories in must be less than calories out.
Exercise will help tone and strengthen the muscles making you feel healthier and in turn allow for more efficient ability to burn that fuel (food) you give yourself.
My DH's heart doc told him 60 min/day to get his body using the extra calories is a good goal. That does not mean if all you have to give is 30 minutes that you should not bother. All movement, whatever the increase will help.
In one of the gyms our sons would go to compete there was a huge banner that read If you rest, you rust...so true.
Good luck with your moving along and healthy eating choices.