Ghrelin and "food noise"

Because ghrelin acts on both the hunger centers and the reward centers of the brain, it can influence not just whether you're hungry, but how much food occupies your thoughts. When these signals are dialed up or poorly regulated, food can feel harder to stop thinking about.

A few things that change ghrelin

• Fasting and dieting raise ghrelin, which is one reason hunger often intensifies when you cut calories — your body is fighting to get the weight back.

• Poor sleep and high stress can push hunger signaling in the wrong direction.

• Weight-loss surgery (like gastric bypass) tends to lower ghrelin, which may be one reason it reduces hunger so effectively.