Final answer:
The description of developing obesity risk over 5 years among a specific population is an example of an incidence rate, which concerns new cases occurring within a designated timeframe.
Step-by-step explanation:
A research article describing the risk of developing obesity among African American youth in County A over 5 years is an example of an incidence rate. This is because it measures the number or proportion of new cases of obesity that occur within a specific time frame among a certain population. Incidence is a critical epidemiological metric used to understand the risk and cause of health-related events and the potential for disease spread. Prevalence, on the other hand, would pertain to the total number of both new and existing cases in the population during a time period, thus providing an idea of the overall health burden of obesity in the population.