70% of today's health care expenditures are for lifestyle-related chronic diseases, such as obesity, diabetes, and heart disease. From Arthritis and the common cold to diarrhea, all encouraged by eating a type of food that is perceived by most to be a healthy staple in our modern diet.
Humanoids have been around for around 7 million years, with the humanlike species of Homo erectus taking charge of the food chain around two million years ago. Our evolutionary peak (physically), as far as brain size, bone density and size, lean muscle mass, etc, was around 10,000 years ago. But from that time, we slowly started to get more sick and more overweight, new diet based diseases started sprouting up, and continue to ravage humans today, on epidemic levels. With the past 100 years seeing even larger spikes in these life-style related diseases (LRD).
What happened 10,000 years ago was the Agricultural revolution.
Our digestive systems have been evolving for millions of years, we have had nuts, seeds, vegetables, fruits and meat for the majority of this time, our bodies have had millions of years to adapt to these slower burning foods. Evolutionarily, grains are very new to us, our bodies have not had time to adapt to both the unfamiliar protein structure of grains and the excessive carbohydrate load of all forms of cultivated grains. When we digest such food, our blood stream gets inundated with glucose(blood sugar). Too much glucose in our bloodstream can be toxic, because of this, our body responds by having the pancreas produce INSULIN. Insulin takes the glucose and stores it away in the liver, muscle, and fat cells. Because it's such an abnormally large carbohydrate hit, our genes respond by producing an excessive amount of insulin.
This is why you see marathon runners who still have plenty of excess body fat, or other people who are fit or strong, yet don't have that defined muscular figure.
As long as we consistently eat foods that trigger our insulin production system excessively, we will promote fat storage and disease, period.
The counter regulatory hormone to insulin is GLUCAGON. Imagine glucagon as a muscularly defined sexy beast of a hormone! Insulin takes glucose and stores it as glycogen for later use. Glucagon's job is to go to the energy storage centers, take the glycogen and use it as energy. This process is called GLUCONEOGENESIS. Excessive amounts of insulin inhibits production of glucagon and thus gluconeogenesis. If you are moving and exercising very often, than your body can use the excess carbohydrates, but if you have an inactive lifestyle and eat many grains, you will most likely become overweight unless you have an incredibly fast metabolism. We have a food pyramid that recommends 9 to 12 servings of GRAINS per day. Couple that with an inactive lifestyle and you get the health epidemic we have today.
This is an updated food pyramid that is far healthier than the one of old. I especially like how the leafy greens have their own section, and it's the first one! Leafy Greens and Vegetables are the BEST FOODS for humans, by far.
I drew information from 'The Primal Blueprint' and 'Wheat Belly', each of which goes into extensive detail on grains and their effects, I recommend both books. Links below:
Blogging site written by Mark Sisson, the author of 'The Primal Blueprint' and one of the more well known 'Paleo' proponents.
http://en.wikipedia.org/wiki/Wheat_belly Link to Wiki page for 'Wheat Belly'
I hope this information has been helpful!