If your dog's diet lacks fat, they can develop several health problems as a result. These include dry, itchy skin, a dull coat, a diminished immune system, heart disease, and diabetes. A lack of a specific fatty acid can cause further problems. For example, a lack of Omega-3 causes neurologic abnormalities and decreased visual acuity. Similarly, a lack of Omega-6 causes weight loss, eczema, susceptibility to infections, and hair loss. Younger dogs may have problems with growth, while mature dogs have problems with reproduction.