I've been undereating for a long time and have made myself quite physically ill. I have brain fog, get dizzy standing up and have fatigue. My GP is quite supportive and I had some blood tests to see if I'm deficient in anything (I'm already under the mental health team so am getting support there). He's told me to eat three meals a day and have 3 snacks which I'm trying to do even though the idea of eating that much food makes me feel ill. My question is how long will it take for the extra food to make a difference? I'm really struggling but if I know it's going to help will try and persevere.