As my patients know, I believe that healthy eating and regular exercise form the foundation of a healthy lifestyle. Arguing that exercise is, “Good for you” may be just as necessary as arguing that the world is round, but here goes! In 1993, a group of epidemiologists from Stanford University School of Medicine published a retrospective study looking at about 10,000 Harvard alumni over 12 years. They found that those who engaged in moderately vigorous sports activity had a 23% lower risk of death. Similarly, in 2007, a group from the National Cancer Institute published an observational study looking at some 250,000 men and women aged 50 to 71. They demonstrated that vigorous exercise (20 minutes three times per week) combined with moderate exercise on most days, resulted in a 50% relative risk reduction in mortality.
The benefits of exercise, of course, are numerous. It is known that exercise lowers cholesterol, increases aerobic capacity, lowers inflammatory markers, lowers blood pressure, and prevents diabetes. There is data suggesting that physical activity may even prevent cancer. For example, in 2012, a group of epidemiologists from the University of Western Australia demonstrated that the risk of proximal colon cancer was 27% lower in a physically active group, compared with the least physically active group. Other benefits of exercise include prevention of osteoporosis, improved mental health, and perhaps even a reduced risk of dementia.
Of course, there are some risks associated with exercise. We have all pulled a muscle here and there, and have, “Thrown our back out.” But more serious risks can include cardiac arrhythmias, heart attacks, severe muscle inflammation, dehydration, asthma exacerbations, and others. So, it is very important that one consults their own physician prior to initiating an exercise program. Your physician will likely check your blood pressure, listen to your heart and lungs, look at your EKG, and in some cases perform a cardiac stress test.
So, how much exercise is enough? When guiding my patients, I like to use the 2008, “Activity Guidelines for Americans” published by the US Department of Health and Human Services. These guidelines use outcomes data in order to prescribe a minimal quantity of exercise. In short, it is recommended that we all exercise at least 500-1000 MET-minutes per week. Are you getting enough exercise? Count your MET-minutes!
OK – so what is a MET-minute? First, allow me explain what a MET is. A MET (Metabolically Equivalent Task) is the factor of energy burned in an activity, compared to rest. For example, light walking burns about twice as many calories as sitting quietly, so it has a MET of 2. Jogging can burn about six times as many calories as sitting quietly, so it has a MET factor of 6. Now, to arrive at MET-minutes, simply multiply the MET factor of your activity by the number of minutes spent doing that activity.
Let’s look at an example. Last week, I went jogging for thirty minutes, on Monday, Wednesday, and Friday. Since jogging has a MET factor of 6, then thirty minutes of jogging gets 180 MET-minutes. At a frequency of three times per week, I arrive at (180X3) = 540 MET-minutes per week. Phew! Just made it!
How many METS should you assign for your physical activity? Here’s a link to help you calculate your MET-minutes:
http://www.topendsports.com/weight-loss/energy-met.htm
Keep in mind that various individual factors may affect the recommended amount of exercise for any individual. For example, those with certain metabolic disorders or diseases, those with severe obesity, those suffering recent cardiac events, and other situations, will affect your own prescription for exercise. Please consult your own physician for more specific recommendations.
Have fun – and keep exercising!
Dr. Van Dam