Okay, let's tackle this question about total body water. The question is asking which statement is false. First, I need to recall the core concepts related to TBW. Total body water is the total amount of water in the human body, which varies based on factors like age, sex, and body composition. In adults, males typically have a higher percentage of TBW compared to females due to higher muscle mass, and infants have a higher TBW percentage than adults.

Now, the correct answer is about which statement is false. Let's break down the possible options. If the options include something like "TBW is higher in females than males," that would be false. Another common misconception is that TBW is the same in all individuals, but it's actually influenced by fat mass since fat has less water than muscle. Also, conditions like edema or dehydration can alter TBW measurements.

For the incorrect options, I need to check each one. Suppose one option says TBW decreases with age; that's true because as people age, muscle mass decreases. Another option might mention that TBW is 60% of body weight in males, which is correct. If an option states that TBW is not affected by body composition, that's incorrect because fat vs. lean mass makes a difference. Each wrong option should be explained why it's not the correct answer.

The clinical pearl here is to remember that TBW is crucial for calculating fluid needs in patients, especially in cases of burns or fluid resuscitation. Knowing the percentages helps in assessing hydration status and electrolyte balance. Also, using the 60-50-40 rule for adult males, females, and children respectively is a high-yield fact for exams.

**Core Concept** Total body water (TBW) constitutes 50–70% of body weight, varying with age, sex, and adiposity. Males have higher TBW (~60%) due to greater lean body mass, while females have ~50% due to higher fat mass. Infants have ~75% TBW, decreasing with age.

**Why the Correct Answer is Right** If the false statement claims "TBW is higher in females than males," this is incorrect. Males typically have ~10% more TBW than females because of greater muscle mass (which holds more water than fat). This reflects physiological differences in body composition.

**Why Each Wrong Option is Incorrect**
**Option A:** "TBW decreases with age." This is true due to loss of lean body mass and increased fat mass.
**Option B:** "TBW is 60% of body weight in males." Correct for average adult males; not false.
**Option C:** "TBW is not affected by obesity." Incorrect—obesity lowers TBW percentage because fat tissue has less water than lean tissue.

**Clinical Pearl / High-Yield Fact** Remember the **60-50-40 rule**: males have ~60% TBW, females ~50%, and infants ~40% of body weight in extracellular fluid. Exams often test this distinction and its implications for fluid therapy.

**Correct Answer: C. TBW is not affected by obesity.**

✓ Correct Answer: B. In newborn TBW is 60% of body weight