Blood sugar disorders can cause fatigue. If your tired your blood sugar is out of control! Excess sugar consumption is one of the major causes for fatigue and many people actually use sugar as medicine. Sugar is addictive creates a cycle of craving and bingeing. Restore your energy by eating foods that are low on the glycemic index. Take a B Complex vitamin to stabilize blood sugar, and also stretching one's body and limbs reduces physical stress and fatigue. Eat lots of fiber too!