Sandy and Molly are best friends who have recently become pregnant. Sandy's BMI is currently 17.5, while Molly has a BMI of 27. Which of the following statements is true?

• A. They should aim to gain the same amount of weight as each other throughout pregnancy.
• B. Sandy should aim to gain more weight than Molly throughout pregnancy.
• C. Molly should aim to gain more weight than Sandy throughout pregnancy.
• D. Sandy's fat intake should increase significantly, while Molly's fat intake should decrease significantly.

Answer: (B)

Verified step by step guidance

1. Understand what BMI (Body Mass Index) represents: it is a measure of body fat based on height and weight, calculated as $\mathrm{BMI}=\frac{\mathrm{weight\; (kg)}}{{\mathrm{height\; (m)}}^2}$.
2. Recognize the BMI categories: a BMI below 18.5 is considered underweight, 18.5 to 24.9 is normal weight, and 25 to 29.9 is overweight. Sandy's BMI of 17.5 classifies her as underweight, while Molly's BMI of 27 classifies her as overweight.
3. Recall pregnancy weight gain recommendations vary based on pre-pregnancy BMI. Underweight women are generally advised to gain more weight during pregnancy to support fetal growth and maternal health, while overweight women are advised to gain less to reduce risks.
4. Apply this knowledge to the problem: since Sandy is underweight, she should aim to gain more weight during pregnancy compared to Molly, who is overweight and should gain less.
5. Evaluate the other options: equal weight gain is not recommended due to different BMI categories, and fat intake adjustments should be balanced and personalized rather than significantly increased or decreased without professional guidance.