Changes in mood can have unpredictable effects on your diet. When feeling down, you might lose your appetite -- or become ravenous and overeat. The same is true for bouts of happiness: Not thinking about food or “happy eating” both can occur. Why? Brain biology and behavioral cues control both mood regulation and hunger signals. And because the same brain signaling that moderates mood also regulates hunger and fullness signals, people often notice that changes in mood also result in changes in food intake -- either eating more or less.