My metabolism will not let me rest. I wish I could gain a little weight. I am lucky if I tip the scale at 100 pounds. I do go to the gym often and I love to ride my bike and walk a lot. I do eat like a piggy sometimes and still no luck on the elephant, and I do love milk !!!
Yes, we have a well documented and long history of people turning into actual pigs and cows because they ate something and rested immediately after. Or not. You might "feel" like a pig for eating too much then resting afterwards (look up food coma), but it will never mutate your dna.