Which of the following factors will not directly affect a person’s weight?

• A. Low levels of leptin in the blood.
• B. Having a specific variant of FTO gene.
• C. Lack of physical activity.
• D. Frequent air travel.

Answer: (D)

Verified step by step guidance

1. Understand the factors that directly influence a person's weight. These include biological, genetic, and lifestyle factors such as hormone levels (e.g., leptin), genetic predispositions (e.g., FTO gene variants), and physical activity levels.
2. Review the role of leptin in weight regulation. Leptin is a hormone that helps regulate energy balance by inhibiting hunger. Low levels of leptin can lead to increased appetite and weight gain.
3. Examine the FTO gene. Variants of the FTO gene are associated with a higher risk of obesity, as they can influence appetite and energy expenditure.
4. Consider the impact of physical activity. Lack of physical activity reduces calorie expenditure, which can lead to weight gain over time.
5. Analyze the relevance of frequent air travel. While it may indirectly affect weight through factors like disrupted sleep or irregular eating patterns, it does not directly influence biological or genetic mechanisms related to weight regulation, making it the correct answer to the question.