We know from week one that the difference between the energy that comes in (food) versus the energy that we burn (being alive, exercising, activity) is the most important factor in us managing our weight. It's a simple concept, but obviously quite complex because of all the factors that influence both of these things.
We are trying to look after our food and nutrition. It's something we can control. We can also try and control how active we are. You might initially think 'I need to get to the gym to get results'. I certainly encourage you to train multiple times a week, but you'll see it's actually your every low level activity which is more important.
If you want to be healthy and manage your weight you need to be active outside the gym. It doesn't have to be anything extreme. Hitting a daily step target will be one of the most important things you do long term.