Lifestyle modification, including weight loss, is the most appropriate next step in the management of this patient who has erectile dysfunction (ED) and is obese. First-line treatments for ED include lifestyle modification (weight loss, exercise, smoking cessation), psychotherapy as needed, and phosphodiesterase type 5 (PDE-5) inhibitors. Randomized controlled trials have shown that obese men who lose weight through dietary changes and exercise experience significant improvement in erectile function compared with obese men who do not lose weight. This patient's sedentary lifestyle has likely contributed to his obesity. He would likely experience improved erectile function as a result of substantial weight loss through healthy diet and exercise. After discussion with the patient, a decision can be made about whether to institute lifestyle changes alone or to combine lifestyle changes with a PDE-5 inhibitor.

Intraurethral alprostadil is more effective than PDE-5 inhibitors at treating ED. However, compliance with intraurethral alprostadil is low, and it is not considered a first-line treatment for ED.

Although it is important to inquire about that status of romantic relationships in patients with sexual dysfunction, this patient reports that his marriage is satisfying; therefore, marriage counseling would not be indicated.

It would be inappropriate to prescribe venlafaxine for depression in this patient who reports that his mood is excellent. Furthermore, venlafaxine is associated with sexual dysfunction.