What is the best and easiest way to stay healthy without spending lot of time?
You do this by developing healthy habits. That way you are not sabotaging yourself by eating unhealthy food out of a box and sitting for hours and hours at your computer.
Get in the habit of eating lots of organic fruits and vegetables. You can maximize this by growing your own. You can grow microgreens on a window sill, layered seasonal lettuces and vegetables in pots on a balcony, or in a 4 x 12 raised bed in your yard.
While growing your own may sound like a waste of time - you can incorporate most of your exercise, so you are saving time you would spend at the gym. And you get the inspiration of growing plants from seeds - its always a way to get perspective on life and its real meaning.