Doug comes from a lineage of obese individuals and is concerned about his own health. He visits his doctor for genetic testing and discovers that he may have a mutation in the gene leptin. Doug is now even more concerned about his own health. Which of the following statements is/are most accurate? I. Doug will surely become obese because of the possible leptin mutation and his family pedigree. II. Doug may be able to prevent obesity with a healthy diet and plenty of exercise. III. Many genes may be responsible for obesity so it is currently not possible to determine whether Doug is destined for obesity. IV. Doug should drown his despair in a shopping trip for larger clothes.