Exercising to stay fit and healthy is wonderful... everyone should do it. Looking at all those Presidential Candidates, from both parties, we can see they all look fairly thin and healthy except for Christie, who is still a bit overweight, but we can see that even he has lost a lot of weight, probably through exercise.
So this is not an exclusive of Obama. GW Bush also played golf and rode bicycles. Ron Paul at his age 6-7 years ago also did a lot of cycling. I could go on and on.
What I'm laughing at is that you respect Obama so much because he exercises. If you told me that he wrote his own speeches or talked without a teleprompter, or was tougher with certain countries in the world then I would understand and I'd probably also admire him, for that.