The body has an intricate monitoring system to make sure levels of glucose are kept steady, even when meals are skipped, etc.
Protein helps moderate swings in glucose levels.
Avoid caffeine and alcohol, too. Stress is a classic source of fatigue. Burn it off with regular exercise. If your symptoms persist, consider asking your doctor for a Glucose-Insulin Tolerance Test. It seems that no matter what we do, we're powerless to avoid disease-causing carcinogens.