In many of our podcasts, articles, and some of my past blogs, the Huffines Institute continues to advocate getting people active. Many times we will use the phrase ‘moderately active’ which is generally interpreted to mean getting at least 30 cumulative mins of activity on a daily basis at a moderate intensity level. Indeed, many studies that have shown positive health effects from daily activity will often use the “30 mins of moderate activity” as a guideline/recommendation. What we forget as Sport Science professionals is that these minimal guidelines are often seen by the public as all they need to do.
Given the general inactivity of most Americans, Sports Science professionals will usually prescribe moderate exercise as a method of getting people moving, believing that once people are regularly active, they will be able and willing to do activity at higher intensities. This approach is generally well supported in the scientific literature because there are several studies that have shown that immediately having previously non-active individuals exercise at too high of an intensity will cause people to stop being active. Thus, prescribing or encouraging exercise that is of too high an effort level at the beginning of an exercise program will actually result in less activity.
Within these limits, it is also important to recognize that the benefits of moderate activity actually can increase exponentially if your exercise bouts are done at a higher intensity level. One new piece of evidence that further supports this was just released by the American College of Sports Medicine and is from Dr. Paul Williams at the Lawrence Berkeley National Laboratory. In one of the largest studies of its kind, Dr. Williams extensively surveyed 106,737 runners (yes, that is over 100,000!) regarding their weekly activity and nutrition practices. I’m often skeptical of studies that ask people to report on how much they’ve exercise or eaten because people will always claim to have healthier behavior than they actually have. In other words, they’ll always say they exercise more or eat less than they do. However, what is unique about this study is that Dr. Williams purposefully surveyed runners. If you’ve ever worked with runners, you’ll know that the large majority of them are obsessive record-keepers. I have a friend that could tell you exactly how far he ran and how long (and a large number of other variables) for any specific date over the last 25 years. This friend is simply representative of the mind-set that most runners possess – there are few that don’t track how much they run and/or what they eat, whether they are in a study or not.
So, it was intriguing that this study surveyed over 100,000 runners. In particular, what was found in this large survey was that exercise seemed to ‘interfere’ with the relationship between nutrition and weight gain. Runners that ate more servings of meat – a behavior that in most populations is linked with increases in weight – did not gain weight. In fact, in several of the analyses, Dr. Williams reported that if exercise was interrupted for a period of time, nutrition again significantly influenced weight. However, with regular high intensity exercise, the relationship between weight and nutrition was non-existent. Thus, if you run, especially more than 2.5 miles per day, you can generally eat what you want (but the more you run, the less effect your diet has on your weight).
While Science tells us that nutrition and exercise both affect weight, it should be kept in mind that these relationships are malleable and are dependent on several variables. This new work slightly tweaks what we’ve known about the weight/exercise relationship and really means that more intense exercise significantly reduces the effect of diet on weight.
So, if you’re not active, go do moderate exercise. If you’ve been active, work on stepping it up to a higher intensity exercise. Not only will your heart benefit, but now there’s even more reason to believe that exercising at higher intensities will drastically change your body weight. Go run!
Until next week, stay active and healthy.
About the Author
Dr. J. Timothy Lightfoot, PhD FACSM RCEP CES, Omar Smith Endowed Chair in Kinesiology, Dept. of Health & Kinesiology, Texas A&M University.