When I go back to school, and if I go for a masters in Health/Fitness I think a decent thesis project just popped into my head.
With endurance athletes whose events last more than a hour part of the strategy is not just keeping them hydrated, but keeping their electrolytes in balance. You can become toxic from water if your electrolytes get out of balance. So when sweating for prolonged time, you lose the sodium.
When a doctor counsels a hypertensive patient one of the first things to cut back on is sodium. Switch to the dash diet, medication, ect ect.
They just released a study where conditioned people and untrained people both ate a cheese burger, fries and soda. Their blood lipids for the first hour was not pretty. But within 90 minutes the conditioned folks had normal blood profiles again, while it took over two hours for the untrained people to return to normal blood profiles. So a similar study already exists. SO on second thought I will probably stay with my original plan.
I am considering a study on sleep apnea. People with disturbed sleep patterns are typically overweight or obese. I hypothesise that even six weeks of very moderate exercise will improve sleep patterns. That alone will add to life span and life quality.
The Original 
I am considering a study on sleep apnea. People with disturbed sleep patterns are typically overweight or obese. I hypothesise that even six weeks of very moderate exercise will improve sleep patterns. That alone will add to life span and life quality. 
