Proteins are necessary for tissue repair and for the construction of new tissue. Every cell needs protein to maintain its life. Protein is also the primary substance used to replace worn out or dead cells. Your muscles, hair, nails, skin, and eyes are made of protein.
Taking supplemental chromium has been shown repeatedly to improve insulin sensitivity and glucose tolerance, even to the point of reversing type II diabetes in many people (1). Thus, as my old clinical nutrition professor pointed out, apparently a chromium deficiency can actually lead to type II diabetes.
This is why, if you struggle with acne, you want to avoid all foods that contribute to insulin resistance (namely sugar and grains), not just the gluten-containing grains. The best way to know if you are insulin/leptin resistant is to measure your fasting insulin level. If it is below 3, you are not likely resistant.