I have been fainting from the very start of my pregnancy but never from eating..mine seems to be the opposite..if I dont eat. The doctor says it's normal and a pregnancy mystery...greeeeat! She and he..I saw two doctors because its pretty worrisome to faint without warning..and both said they cant explain it or do very much about it.
Just don't get up too fast, especially if you have been sitting for some time. Make sure you eat, even small meals (apples are VERY good for this, as they have tons of vitamins) and get lots of sleep.
I would ring your midwife/doctor though because fainting when eating seems odd..
Are you maybe waiting too long to eat? I know sometimes if I wait too long to eat, I get very sick to my stomach and my head goes very fuzzy. But yet I am not having any other 'hunger' signs, such as my stomach isnt grumbling...I dont feel hungry. I dont know...
Sorry I cant be more help!