In the Jan/Feb issue we challenged any notion that high intensity exercise was not beneficial to you, an idea that germinated in the media after the publication of a study in the Journal of the American College of Cardiology that was not suggesting that at all. The study found similar lifespans in people who run intensely and people who remain sedentary (and increased lifespans in those who exercise more moderately). But the widely reported conclusion that a high level of running has the same effect as no running at all is very problematic, as we discussed at length in “Is High Intensity Running Bad for You?”
Now, a study from Ontario, Canada published in the Annals of Internal Medicine has found a benefit from high intensity exercise specifically: improved glucose tolerance.
The researchers looked at both amount and intensity of exercise in various combinations and then measured abdominal obesity and glucose tolerance in 300 obese adults. All types of exercise in the study resulted in improved waist circumference. But only intense exercise resulted in reductions in blood glucose levels.
For 24 weeks the subjects participated in five weekly sessions of either:
a short duration at 50% VO2max
a long duration at 50% VO2max
a long duration at 75% VO2max
Session length was determined by calories burned. For men in the 50% VO2max groups (low intensity), exercising for a short duration meant burning an average of 300 kcal; for women, 180 kcal.
Interestingly, the amount of calories burned in the long duration groups—whether low or high intensity—was the same: 600 kcal on average for men, 360 for women.
The average session length was 31 minutes for short duration, low intensity; 58 minutes for long duration, low intensity; and 40 minutes for long duration, high intensity.
It is also noteworthy that body weight and waist circumference improved similarly across all active groups, regardless of intensity or duration of exercise. The average decrease in waist circumference for both long duration groups matched, at 4.6 cm; for the short duration, low intensity group it was 3.9 cm.
It was glucose tolerance, as measured by a glucose tolerance test administered two hours after activity, that improved significantly only in the high intensity, long duration group. Reductions in blood glucose in the other groups were negligibly similar to the control group.
Duration of exercise is important, and sustaining physical activity for up to an hour even at a low or moderate intensity should be the first priority for anyone new to a workout program. This kind of activity is an attainable and sustainable form of physical fitness, perhaps the two most important traits in the early-going stages of a regimen, as they will ultimately determine whether a sedentary person sticks to a new good habit. But it is wise to also remember that how intensely you exercise does matter, and with a little inner push—or a touch of an incline button on a treadmill—you can lower your blood sugar level, along with achieving reductions in abdominal obesity and body weight.
In February the U.S. Dietary Guidelines Advisory Committee (DGAC), which is appointed by the U.S. Department of Health and Human Services and the U.S. Department of Agriculture, announced that limiting dietary cholesterol will no longer be recommended. The change in this guideline definitively puts to rest, at least for now, a longstanding but also long-questioned belief that ingesting foods high in cholesterol would lead to health problems, including coronary heart disease (CHD).
What is and isn't controversial
This change is broad and significant, but not controversial. We know that the great majority of the body's cholesterol is manufactured in-house, as it were, and not so much acquired from dietary cholesterol intake.
The real dietary controversy that has emerged this year stems from the publication of a review and meta-analysis of all the existing clinical trial data on fat consumption, unleashed in the BMJ-affiliated journal Open Heart. This extensive work examines correlations between dietary fat intake, serum cholesterol levels, CHD and all-cause morality.
Serum cholesterol, as opposed to dietary cholesterol, has long been held up as a major indicator of CHD risk. This is bodily cholesterol—what is actually circulating in the blood, and it is listed as one of the six major risk factors identified by the exhaustive Framingham Heart Study, widely acknowledged as a premier longitudinal study. Begun in 1948, it continues today, looking across decades at men, women and children in Framingham, MA, and it is now on its third generation of participants. (continued)
Kenneth Cooper, MD
Jack Daniels, PhD
Randy Eichner, MD
Mary Jo Feeney, MS, RD
Mitchell Goldflies, MD
Paul Kiell, MD
Sarah Harding Laidlaw, MS, RD
Paul Langer, DPM
Douglas Lentz, CSCS
Todd Miller, MD
Gabe Mirkin, MD
Col Francis O’Connor, MD
Stephen Perle, DC, CCSP
Pete Pfitzinger, MS
Charles L. Schulman, MD
Bruce Wilk, PT, OCS
Mel Williams, PhD
Michael Yessis, PhD
Jeff Venables, Editor
board of directors
Jeff Harbison, President
Bill Young, Secretary-Treasurer
(Vacant) Vice President
Charles L. Schulman, MD, AMAA Pres.
Terry Adirim, MD, MPH
Senator Bill Frist, MD
Ronald M. Lawrence, MD, PhD
Noel D. Nequin, MD
Executive Director: Dave Watt
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