Diet is a risk factor in several medically important disease states, including obesity, celiac disease, and functional gastrointestinal disorders. Modification of diet can prevent, treat, or alleviate some of the symptoms associated with these diseases and improve general health. It is important to provide patients with simple dietary recommendations to increase the probability of successful implementation. These recommendations include increasing vegetable, fruit, and fiber intake, consuming lean protein sources to enhance satiety, avoiding or severely limiting highly processed foods, and reducing portion sizes for overweight and obese patients.