After eating I feel nauseous and very tired. Is that normal?
That is possible. You probably suffer from dumping syndrome. Dumping syndrome is a term collectively used for symptoms that occur immediately or a few hours after eating. These symptoms may occur after eating or drinking too fast, eating too large portions, eating (too) many sugars. Typical complaints are nausea, lethargy, dizziness, sweating, cramps, diarrhoea, accelerated heartbeat, etc. To avoid dumping syndrome, it is recommended to eat calmly and chew properly, not to drink during or immediately after meals, to eat small portions, to avoid fatty meals and to limit sugary foods. If the symptoms recur regularly, consult your doctor.