A report published in Lancet Diabetes and Endocrinology has called for an overhaul of our understanding of obesity. An over-reliance on using Body Mass Index [BMI]as a metric has the peculiar effect of leading to both underdiagnosis and overdiagnosis of the condition. __________________________. BMI does not give accurate information about how fat is distributed in an individual’s body. It frequently fails to capture the true state of health of an individual. A person’s BMI may indicate they are “obese”, but their organs and bodily functions may be absolutely normal. Every individual is a unique constellation — not only of genes and other biological variables, but also socio-economic conditions and habits.

The passage given critiques the use of BMI as a reliable metric for diagnosing obesity and emphasises its limitations. We therefore need a sentence in the blank that directly explains why BMI is problematic, while also logically linking the critique to the details about fat distribution and health that follow in the subsequent lines.  

Option A contradicts the paragraph’s central claim by suggesting BMI can pinpoint the cause of obesity. Option B shifts the focus to social media, which is unrelated to the current discussion. Option C implies that BMI is used to prescribe treatment, which the paragraph does not suggest. Option D correctly extends the idea and supports the critique of BMI’s effectiveness. It connects the idea of misdiagnosis to the root issue with BMI, setting up the explanation that follows about how BMI fails to accurately reflect fat distribution and overall health, thereby maintaining the argumentative flow.

The correct answer in this case is therefore option D.