Refined grains are unhealthy because the milling process, which is designed to increase a product's shelf life, strips out healthy fiber and nutrients that have been shown to decrease the risk of heart disease, certain cancers, type 2 diabetes and more, according to the Mayo Clinic. Additionally, individuals who consume a diet rich in whole grains rather than refined carbohydrates generally are healthier and live longer, according to WebMD.
Eating refined grains can also take a toll on the waistline, because they do not contain the fiber that can make the body feel full. In fact, one study in the Journal of Nutrition found that individuals who consume whole grains at least three times per day have less abdominal fat, according to Eating Well magazine.
Refined grains are also typically higher on the glycemic index than their whole-grain counterparts. High glycemic foods can cause blood glucose levels to spike, which, in turn, can speed fat production, increase calorie consumption and drop insulin sensitivity, according to Scientific American. Whole grains are digested more slowly than refined grains, which keeps blood sugar levels even, and avoiding these peaks and valleys can help lower the risk of type 2 diabetes, according to WebMD.