Food is important to Jacob in both strands of this story. When he's young and has little money, he's desperate for decent food. Don't forget, this is during the Depression, when lots of people didn't have enough to eat. (That's why the lower-class circus workers get so upset when Uncle Al stiffs them on their paychecks. They really, really need that money.) So when Jacob first hooks up with the circus, he's excited to be able to eat a full meal:
I grab a plate and scoop up a mountain of potatoes, eggs, and sausages, trying to keep from looking desperate. The scent is overwhelming. I open my mouth, inhaling deeply – it's like manna from heaven. It is manna from heaven. (3.60)
Not everyone gets such "heaven[ly]" food. At times Jacob has to watch helplessly while others go hungry. That doesn't bother people like August, who have no problem chowing down in front of the less fortunate. It seems to bother Marlena more than anybody else. She gives food away or refuses to eat if others are going hungry.
Later in life, Jacob still covets good food. In the nursing home, he gets angry that the old people are fed a restricted diet:
"What?" I say loudly. "Is that so much to ask? Doesn't anyone else here miss real food? Surely you can't all be happy with this … this … pap?" I put my hand on the edge of my plate and give it a shove. (5.58)
Jacob values "real food" because it was so important in his early life. It's ironic that he lived through the Depression, a time when food shortages were very real, only to find himself in a time and place where food is plentiful but doctors and nurses seem to be arbitrarily restricting it. Great food has become a long-lost pleasure, something to dream about: "I just like to weigh the options, as though I were standing in front of Solomon: a final roll in the hay or an ear of corn. What a wonderful dilemma" (1.24).
Tellingly, Jacob makes a biblical comparison here, linking food to the wise judge Solomon. (Earlier he linked it to heaven.) It seems as if great food can only come from God. When Rosemary brings Jacob something appetizing to eat at the end of the first chapter, it's an apple. Could there be a more Biblical food?
All in all, food in this story reminds us that life just isn't fair sometimes. Some people have food and others don't, through no fault of their own.
See "What's Up With the Title?" for more on this. (No need to repeat: yay, Internet!)