In addition to simple sugars, beware of processed or refined foods as they are more difficult to break down in digestion. What's more, the food's molecular structure has changed, robbing it of its true nutrients.
Processed and refined foods are higher on the glycemic index, a scale that ranks carbohydrate-rich foods by how much they raise blood glucose levels.
Foods high on the index burn quickly and release a rapid shot of energy to the body. Again, this is not good for stamina and leaves the body in a crash state.
Foods low on the glycemic index release energy more slowly and combat fatigue. Low index foods are typically lower in calories and fat and higher in fiber.