"Put the fork down" is easy advice, but for many it's a lot more challenging than it sounds.
For me, and I suspect a lot of people, focusing on exercise first is the key. I can plot the number of miles I post on the bike against my weight. Of course I absolutely do more than 300 minutes a week on the bike.
Diet is super important, likely more important that fitness, but diet is vastly more difficult for me. Also, when I'm working out regularly, my diet naturally shifts. If I'm sitting at my desk or on the couch for weeks at a time, food intake increases.
I'm sure if I could ever properly reign in my eating I could change this, but I've tried so many times and it never works. Working out on the bike does, and as I mentioned above, the intake adjusts correctly when I do it.