John has a lot of good info in video's on here.  But, if you don't have time to watch all of them, John does a good job of giving you the cliff notes on what's going on.  Basically boils down to sugar is not good for the body.  Some can tolerate more than others without issues.  If something is high carb it's high in sugar.  

I cut down on bread, milk, sweet tea and soda and it made a huge difference.  I didn't think I was overweight, but then looking at where I should be I was.  I lost 40lbs.  217 was the most I ever weighed and dropped to 177.  I went off the diet somewhat for a while and have been hanging around 190.  I was dragging ass all the time before.  I have a lot more energy now, even more when I was under 180.  Since the kids and wife have been home on extended summer break that really put a damper on my diet as we have a big lunch and supper.  I used to eat just a bit of meat for lunch and that was it. I skip breakfast as an intermittent fast, don't even miss it. Instead of being hungry at 10 am I make it to 11 now before hunger slightly sets in.