Imagine you're a public health researcher and you've been asked to design an exercise-related study to explore the association between obesity in childhood and adverse health outcomes in adulthood. Specifically, you are interested in understanding the effects of exercise and weight loss in childhood on the risk of cardiovascular events and premature mortality later in life. Consider the following study designs and compare their respective feasibility, advantages, and disadvantages.

1. A randomized control trial:
   1. A study group of 300 children aged 10-15 years old will be recruited and randomized to no (control), low, or high intensity exercise groups. Eligible children will be sedentary (no history of high intensity exercise), without prevalent diabetes or history of other chronic conditions (such as asthma) that might inhibit exercise adherence. Participants undergo a baseline clinical assessment and will be followed up with biannual clinic assessments of BMI, blood pressure, and fasting glucose level until death or age 40. The exercise intervention consists of a four-week session in the 1^st and 2^nd years of the study.
   2. A cohort study
   3. A cohort of 2000 children aged 5-18 will be recruited. Eligible children will have no history of prevalent diabetes. Participants will undergo an initial clinical assessment and answer a baseline questionnaire about exercise habits, health conditions, diet, and other important demographic and clinical factors. Participants will be followed up with biennial questionnaires about their health and exercise habits, as well as a self-administered oral glucose tolerance test, until either death or age 55.

Total cost per year per participant to initiate and maintain the randomized control trial will be approximately 15 times the cost of the cohort study.