I feel sick whenever I eat. What could be the problem?

I get really bad head rushes whenever I stand up and I feel like I am going to faint every time I eat well and drink a lot of water so what's the problem?

• Answer:

  There are two types of nervous system in the body: the type that makes you move your arm volontarily, like when you're typing at your keyboard, or playing a sport. But there's also an 'autonomic' nervous system, which as you can guess from the name, is 'automatic', and looks after things such as digestion, heart rate and breathing (although breathing can be controlled actively), continence, etc. This autonomic is separated into two types of activity: one is called sympathetic, and one is parasympathetic. When you are scared and alert, or stressed, the sympathetic will take over, increasing your heart rate, breathing rate, making your muscles more tense, and raise your blood pressure. But when you eat a lot, and so as to mobilize your body's energy where it's needed, the parasympathetic nervous system kicks in, and draws blood to your digestive organs, lowers your heart rate and blood pressure. The intricate functionality is a difficult balance that most of the tame is rather well regulated by our bodies. In your case, and in the case of many others like yourself, after a hearty meal your body's turning it's attention to digesting. So, when you get up, you can feel dizzy, hazy, and the symptoms are likely due to the lowering of your blood pressure, and therefore less blood reaching your head, as if you were fainting.