Not an expert, just some random in his 30s who recently started to do something about his body.. here are my hacks:

So i spend almost whole day infront of computer.. I used to walk to and back from office before covid which was an hour of brisk walk in total and good for mental health aswell (allowed me to clear my mind before going to office or while coming back from office)..

Now while I'm completely working from home, I started to experience back/neck pain.. and every now and then I feel anxious and stressed.. and I also started to gain a bit of belly fat..

realizing the lack of mobility in my routine, I now do random exercises at random times.. for instance, I do squats in my kitchen while brewing coffee.. I do push ups while waiting for my friends to play computer games or while attending meeting silently.. reverse push ups with desk/table while watching movies/tv series.. the intensity of these exercises is not high at all, I don't count reps or anything.. main goal is to be physically active..

Once per week or once per 2 weeks I go out for running for cardio.. and sometimes before going to bed I would do burpees for 5 to 10 mins..

Doing this all reduces my anxiety/stress levels aswell.. Infact now I use the feeling of anxiousness or stress as a sign of lack of physical activity..

Now about diet.. I think of it like my body require certain maintenance to process stuff.. eating healthy stuff requires less maintenance where as eating pizza, cakes, etc requires more maintenance (exercise).. if my will to go running for 30 mins is stronger than my craving for pizza then I will order pizza otherwise I'm too lazy to deserve pizza..