Wheat contains starch, which is fine, but along with starch there is gluten, a complex of proteins that has been linked to a variety of diseases, and wheat germ agglutinin, a lectin antinutrient designed to protect the plant seed from consumption. Celiac disease, obesity, diabetes and mental illness have all been linked to wheat consumption.
The problem in wheat is proteins, not the carbohydrate. White flour is dense with these problematic proteins and antinutrients. Wheat causes problems even in popultations who've been eating it for thousands of years.
Stick with potatoes, sweet potatoes or root veggies for your starch, and stop eating bread, cookies, cakes and other baked goods.
Fructose is a carbohydrate, but metabolically it is quite different from the glucose that comes from starch. In small amounts or in moderate amounts in real food, fructose is not a problem, but the ubiquity of fructose in the modern diet creates obesity, insulin resistance, fatty liver disease, and abnormal bacterial growth in the gut with consequent inflammation.
Fructose is easily minimized by simply refusing to eat processed food that comes in a box (especially 'low fat' foods), and by refusing to drink caloric drinks like soda pop and fruit juices and sports drinks.
Excess Linoleic acid
Linoleic acid is an omega 6 fatty acid, a polyunsaturated fat or PUFA. Along with n-3, the other type of PUFA, it is technically an essential fatty acid, but the actual requirement is so small it might be better considered a micronutrient. A hunter-gatherer or paleolithic human might have had a total PUFA intake of 3% of calories. Modern north americans have a PUFA intake of around 15%, most of it due to n-6. The problem with this is twofold:
1) As n-3 and n-6 precursors compete for the same enzyme in the eicosanoid pathway, the excess of n-6 in the diet means that n-3 is outcompeted at the enzyme level. The result is a preponderance of inflammatory signalling molecules. Increased cancer and inflammation - both too little and not enough immune activity - are both likely related to this.
2) Many are aware that 6:3 ratio of fatty acids is important, so they try to compensate by taking fish oil to balance the ratio. This doesn't really work to well - you can't realistically eat that much fish, and if you take fish oil supplements, you exacerbate the second, more important problem. Your total PUFA intake is now evan higher and total PUFA, especially including the added highly unstable n-3, leads to oxidative damage to your cells. Your arteries, liver and other organs are not happy. Your insulin resistance and other metabolic control systems may become disturbed.
The way to correct the modern excess of n-6 linoleic acid is to avoid the modern sources of it. Stop eating all temperate vegetable oils and veggie oil fried food- cooking and frying oils like corn, soy, canola, flax, all of it. And go easy on the nuts and factory chicken. These are big sources of n-6, especially the nuts and nut oils."
Article in its entirety: http://www.psychologytoday.com/blog/p-nu/201103/dietary-manifesto-paleo-20
Doctor Kurt Harris' blog: http://www.paleonu.com/