**Core Concept**
The World Health Organization (WHO) defines obesity and overweight categories based on body mass index (BMI), which is calculated by dividing weight in kilograms by the square of height in meters. BMI is a widely used indicator of weight status, and its categories are essential for diagnosing and managing obesity.

**Why the Correct Answer is Right**
According to the WHO, a BMI of 25 or higher is classified as overweight, while a BMI of 30 or higher is classified as obese. This classification is based on the association between BMI and increased risk of chronic diseases such as diabetes, cardiovascular disease, and certain types of cancer. The WHO BMI classification is widely accepted and used globally for public health purposes. The correct answer highlights the importance of BMI in assessing weight status and its implications for health.

**Why Each Wrong Option is Incorrect**
**Option A:** Dexenfluramine was a serotonergic anorexiant that was withdrawn from the market due to concerns about its safety and efficacy. It is not considered a drug of choice for obesity treatment.
**Option B:** Sibutramine was a norepinephrine and serotonin reuptake inhibitor, not just an epinephrine uptake inhibitor. It was withdrawn from the market in 2010 due to concerns about cardiovascular safety.
**Option D:** Long-term effects of orlistat, a lipase inhibitor, are not well established. While it is effective for short-term weight loss, its long-term efficacy and safety are still being studied.

**Clinical Pearl / High-Yield Fact**
BMI is a simple and widely used measure of weight status, but it has limitations, such as not accounting for muscle mass or body composition. Clinicians should consider other factors, such as waist circumference and skinfold measurements, when assessing patients with a BMI in the overweight or obese range.

**✓ Correct Answer: C. According to WHO body mass index greater then 25 is overweight**