I had the mumps when I was four, nearly died, and was very, very skinny. At that point, it became my mother's mission to fatten me up, and she was successful.
food meant love.
Even as I kid, I was eating "Farmer's Breakfasts" with eggs, bacon, sausage, and toast. Sandwiches always had a ton of Hellman's mayo, cheese, and salami. We had homemade potato salad with lots of mayo in it. We even had a side of mayo with our homegrown tomatoes and cucumbers. Mayo. That is one quick way to add some serious calories. My whole family was large.
Also, my father used to say, "eat up kids, you don't know when the next meal will be." That mantra stuck with me for a long time, despite acknowleging it and rationally observing it has no basis in truth.