1. Sugary foods, like soda or candy, can make you feel spaced-out, weak, confused, or nervous once the glucose in your brain drops — this is also known as a sugar crash.
2. Heavy, calorie-ridden foods like hamburgers and fries will make you sleepy and slow you down at work.
3. Eating too little can make you process information more slowly, take longer to react and have more trouble remembering sequences.