**Core Concept**
The management of obesity involves a combination of lifestyle modifications, behavioral interventions, and pharmacological therapies. The goal is to achieve and maintain a healthy weight through a reduction in caloric intake and increase in physical activity.

**Why the Correct Answer is Right**
Orlistat, a gastrointestinal lipase inhibitor, is a commonly used pharmacological agent in the treatment of obesity. It works by inhibiting pancreatic lipase, an enzyme responsible for the breakdown of triglycerides into fatty acids and glycerol. By reducing fat absorption, orlistat leads to a decrease in caloric intake and subsequent weight loss.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because sibutramine, a norepinephrine and serotonin reuptake inhibitor, was withdrawn from the market due to cardiovascular concerns. Although it was used to treat obesity, its potential risks outweigh its benefits.
**Option B:** This option is incorrect because rimonabant, a cannabinoid receptor antagonist, was also withdrawn from the market due to psychiatric side effects, including depression and anxiety. Its potential benefits were not sufficient to outweigh its risks.
**Option C:** This option is incorrect because metformin, an antidiabetic medication, is not a primary treatment for obesity. While it may have some beneficial effects on weight loss, it is not a first-line therapy for this condition.

**Clinical Pearl / High-Yield Fact**
When prescribing medications for obesity, it is essential to carefully evaluate the patient's medical history, including any pre-existing cardiovascular conditions, psychiatric disorders, or other comorbidities. This helps to minimize potential risks and maximize the benefits of therapy.

**Correct Answer: C. Metformin is not a primary treatment for obesity.**