Kate Gosselin feels best when she runs 10 miles every other day, according to Us Weekly. But what the 37-year-old mother of eight doesn't know is that when it comes to vigorous exercise, more isn't always better. Turns out, people who work out too hard for too long may be less healthy than sedentary people, and are more likely to die than moderate exercisers, according to an editorial recently published in the British journal Heart.
The editorial authors reviewed decades' worth of research on the effects of endurance athletics. They found numerous studies that showed that moderate exercise was good, but excessive exercise was damaging. For instance, in one German study published in European Heart Journal, researchers compared the hearts of 108 chronic marathoners and sedentary people in a control group. Surprisingly, the runners had more coronary plaque buildup, a risk factor for heart disease.
In another observational study, researchers tracked over 52,000 people for 30 years. Overall, runners had a 19 percent lower death risk than non-runners. However, the health benefits of exercise seemed to diminish among people who ran more than 20 miles a week, more than six days a week, or faster than eight miles an hour. The sweet spot appears to be five to 19 miles per week at a pace of six to seven miles per hour, spread throughout three or four sessions per week. Runners who followed these guidelines reaped the greatest health benefits: their risk of death dropped by 25 percent, according to results published in the journal Medicine & Science in Sports & Exercise. (Are you ready to start running, or start again after a long layoff? Use our 4-Week Beginner Running Plan.)
Forget about chafing and sore muscles: excessive exercise can cause even more serious wear and tear on your body. During a strenuous workout, your body works hard to burn sugar and fat for fuel. And just like burning wood in a fire, this creates smoke. The "smoke" that billows through your system is actually free radicals that can bind with cholesterol to create plaque buildup in your arteries, and damage your cells in a process known as oxidative stress. (Eating antioxidant-rich foods like berries can help you recover from hard workouts. That's why they made our list of The 10 Best Fitness Foods.)
"Your body is designed to deal with oxidative stress that comes from exercise for the first hour," says cardiologist James O'Keefe, MD, Director of Preventative Cardiology at the Saint Luke's Mid America Heart Institute in Kansas City, and author of the Heart editorial. "But prolonged intense exercise causes excessive oxidative stress, which basically burns through the antioxidants in your system and predisposes you to problems."
However, O'Keefe insists that this is no excuse to trash your running shoes and take to the couch. "Exercise may be the most important component of a healthy lifestyle, but like any powerful drug you've got to get the dose right," he says. It's true: exercise--in moderation--can reduce your risk of heart disease, high blood pressure, type 1 diabetes, Alzheimer's, dementia, obesity, and premature aging. Regular workouts can also promote muscular health, skeletal health, and boost your mood. Overdo it, though, and many of these health benefits practically vanish.
More: 6 Benefits of Running