Just a quick question.

Eat like a pig.

Be totally inactive.

If you feel you're under weight, this isn't the answer. You'll want to exercise and build up muscle which helps you build weight and definition. You can eat more calories than required per your weight, for weight increase which is much better than being unhealthy.

But to answer your question: Stop exercising, eat greasy foods and unhealthy foods, eat less meals per day (ie 1 big instead of 3 smaller ones).