"Look at the people you consider old, and I bet over 80 percent of them are bent over," Sam says. In fact, the average guy will lose nearly 2 inches of height by the time he hits 60, and another inch by the age of 70. Sam's theory is that when your body is hunched, your organs are compressed, and so are your blood vessels. "When your blood vessels are compressed, you're just asking for trouble," he says. "The time to start standing up straight is when you're 30, not 60."