As I have said repeatedly in the past, it is best not to wait until the zombies come to begin practice and preparation.
Your body is a tool that responds to the training you give it. If you tell it to store lots and lots of body fat, it will get really good at doing exactly that, and will continue to do so as long as it receives the necessary stimulus.
If you tell it to build muscle, it will only do so as long as it receives the necessary stimulus. It just so happens that Lent just started for the year.
Give your body exactly what it needs, and nothing more. for the next 40 days plus Sundays, give your body meat, produce, and nothing else.
Give it push-ups, jumping jacks, burpees, sit-ups, and hard 3-mile runs.
If you can't do that for the next 40 days, you had better make preparations to be in the first wave that dies after the zombies come.