Final answer:
The ability to float is influenced by an individual's body density, with muscular people generally being denser and therefore potentially less buoyant than obese individuals who have a higher body fat content that is less dense than water. The buoyant force is responsible for this floating effect, and BMI alone isn't a precise measure of body fat or health risk.
Step-by-step explanation:
When it comes to floating in water, the difference between a muscular person and an obese person largely depends on their body density. Since muscle is denser than fat, a muscular person will typically have a greater body density and may have a harder time floating than an obese individual, who likely has a higher percentage of body fat, which is less dense than water. Regarding the support in the fluid, both muscular and obese individuals are buoyed by the water, and the buoyant force is what makes objects float or sink based on their density in relation to the fluid.
Moreover, understanding body density is essential in medical diagnostics and athletic training. Techniques like underwater weighing can help determine body composition, given that bone and muscle weigh more than water, making someone with more muscle mass heavier in water. However, fat does not weigh more than water, hence why those with higher body fat percentage tend to float better.
In the context of body mass index (BMI), it's important to know that BMI has limitations as it does not consider fat mass or fat distribution. This means that BMI might not accurately reflect the amount of body fat or predict health risk as well as other measures. Still, it is a widely used tool to categorize general health.