**Core Concept**
Bariatric surgery is a treatment option for obesity and related comorbidities. It involves surgical modifications to the digestive system to restrict food intake or alter nutrient absorption. The primary goal is to achieve significant weight loss and improve or resolve associated health conditions.

**Why the Correct Answer is Right**
Bariatric surgery is generally recommended for patients with a body mass index (BMI) of 40 or higher, or for those with a BMI of 35-39.9 who have at least one obesity-related comorbidity, such as type 2 diabetes, hypertension, or sleep apnea. The surgery is most effective for patients who have tried and failed to achieve significant weight loss through lifestyle modifications and medical interventions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because bariatric surgery is not typically indicated for patients with a BMI below 35, unless they have a severe obesity-related comorbidity.
**Option B:** This option is incorrect because bariatric surgery is not typically indicated for patients with a history of substance abuse or eating disorders, as these conditions can increase the risk of complications and poor outcomes.
**Option C:** This option is incorrect because bariatric surgery is not typically indicated for patients with a significant psychiatric comorbidity, such as severe depression or anxiety, unless these conditions are well-managed.

**Clinical Pearl / High-Yield Fact**
It's essential to note that bariatric surgery is a highly effective treatment for obesity-related comorbidities, but it's not a substitute for lifestyle modifications and medical interventions. Patients who undergo bariatric surgery must adhere to a comprehensive post-operative care plan to ensure optimal outcomes and minimize complications.

**Correct Answer: D.**