What is diabetes? What's the difference between type 1 and type 2 diabetes? Which, if either, is genetic and which is caused by lifestyle factors?

Diabetes is when the body can't control its blood sugar levels (the sugar in the blood). Which can result in there being too much sugar, or too little sugar (I was wrong - 2013). Which is the difference between type 1 and type 2, I think. I'll have to check.

It says type 2 is when the body can't use insulin 'for unknown reasons', even though the insulin is in normal supply. Later, insulin production decreases (because the body 'realises' the insulin is going to waste?). Type 2 is by far the most common type of diabetes, at 90-95% of all diabetes cases. It's linked with obesity: 'about 80 percent of people with type 2 diabetes are overweight.'

Type 1 diabetes is caused when the body's own immune system destroys the insulin-production cells (the beta cells in the pancreas). Again, the scientific reasons for this are unknown. Perhaps there are different ways it could happen, e.g. a genetic fault in the immune system, or the beta cells, which would theoretically make them antigenic.

What does insulin do?

insulin forces storage of glucose in liver (and muscle) cells in the form of glycogen; lowered levels of insulin cause liver cells to convert glycogen to glucose and excrete it into the blood. Wikipedia

So low insulin means less storage of glucose, and more blood glucose. Wouldn't this make you feel hyper and energetic though - like having drunk a bottle of sugary cola?

I've looked on wikipeda for the symptoms, and it says the main ones are frequent urination, thirst and hunger. No hyper behaviour then.

My brother tells me a kid at his school had diabetes, and he fainted in the playground. I don't understand why - unless he somehow had low blood sugar? From taking too much insulin? Also, he had to eat lots of sugary snacks throughout the day, every day. Why?? He has diabetes, his blood sugar level should be too high!

According to this site, there is something called insulin resistance. It says it happens when too much insulin is produced. This sounds like rubbish to me. Insulin resistance is when the body is resistant to the effects of insulin - i.e. type 2 diabetes, which we found out about earlier on.

Therefore, I haven't found out why my brother's diabetic friend had to eat lots of sugary food, contrary to logic. Apparently my google search is inadequate. It's frustrating when real-life experience can't be explained using the internet, but somehow reassuring too.