I WILL WRITE HOW I WANNA WRITE MIND YOUR OWN BUISINESS!
A sluggish feeling after meals is associated with overeating. If you're not already, try eating small meals more often through the day, and I agree that eating high fat will do it too. What happens is that when we overeat, the blood rushes to the gut to digest all that food and there's less blood to the brain and rest of the body.
Many times fatigue following meals is due to the intake of fatty foods (not sugar) and a substance your body secretes to digest them. Doctors call the weak, sleepy feeling "alkaline tide". Try a large fat-free or low fat meal and compare how you feel afterwards with your regular meals. Alkaline tide is not a disorder, however some people are more sensitive to the process than others. Hope this helps
Maybe it is poor digestion. There is a great natural product called synergy for helping with digestion. I also know a number to call on Tuesday and Wednesday nights called "ask the doctor" there is no charge except your long distance call. If interested in more information email me at ***@****