Correspondence
Effects of Exercise on Plasma Lipoproteins
N Engl J Med 2003; 348:1494-1496April 10, 2003
- Article
To the Editor:
In the Studies of Targeted Risk Reduction Interventions through Defined Exercise (STRRIDE), reported by Kraus et al. (Nov. 7 issue),1 investigators found that exercise had a substantial dose-dependent effect on the lipid profile. Because there was only a small (≤1.5-kg) reduction in body weight, they conclude that these changes are not dependent on weight loss. However, they do not take into account the possibility that there may have been relevant changes in total body fat. Intense physical exercise would be expected to result in a noticeable increase in lean body mass (specifically, skeletal-muscle mass), with a proportional decrease in body fat (and minimal change in body weight).2 In addition, increased physical activity can reduce total body fat, with a preferential effect on abdominal adipose tissue.3
It is therefore not clear whether the beneficial effects of exercise demonstrated by Kraus and coworkers were mediated by changes in total body fat or body-fat distribution. It may be wrong to conclude that a reduction in weight (or rather body fat) is not important for an exercise-mediated improvement in the lipid profile.
3 ReferencesArya M. Sharma, M.D.
McMaster University, Hamilton, ON L8L 2X2, Canada
sharma@ccc.mcmaster. ca 1
Kraus WE ,Houmard JA ,Duscha BD , et al. Effects of the amount and intensity of exercise on plasma lipoproteins. N Engl J Med 2002;347:1483-1492
Full Text | Web of Science | Medline2
Garrow JS ,Summerbell DC . Meta-analysis: effect of exercise, with or without dieting, on the body composition of overweight subjects. Eur J Clin Nutr 1995;49:1-10
Web of Science | Medline3
Thomas EL ,Brynes AE ,McCarthy J , et al. Preferential loss of visceral fat following aerobic exercise, measured by magnetic resonance imaging. Lipids 2000;35:769-776
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To the Editor:
The excellent study by Kraus et al. is a reminder that the beneficial effects of exercise are dose-dependent not only with respect to lipid metabolism, but also with respect to the compliance of study subjects. The dropout rate of 39.6 percent (including 30.2 percent of randomized subjects who dropped out of the study and 9.4 percent who had an excessively low rate of adherence to exercise) was similar to that in the pilot study,1 in which the low-amount–vigorous-intensity group had the highest dropout rate (52 percent) among the exercise groups. This finding affirms the general recommendation to increase the amount, rather than the intensity, of exercise. Saving exercise time by implementing vigorous training regimens may not be the best advice.
1 ReferencesArno Schmidt-Trucksäss, M.D.
University Hospital, 79100 Freiburg, Germany
schmidt@msm1.ukl. uni-freiburg. de 1
Kraus WE ,Torgan CE ,Duscha BD , et al. Studies of a Targeted Risk Reduction Intervention through Defined Exercise (STRRIDE). Med Sci Sports Exerc 2001;33:1774-1784
CrossRef | Web of Science | Medline
To the Editor:
The mechanisms underlying the association between physical activity and a decrease in cardiovascular events are not entirely understood. Kraus et al. report that exercise is associated with a graded beneficial effect in several plasma-lipoprotein variables. This finding, as discussed in the accompanying editorial by Tall,1 could explain why the risk of cardiovascular events progressively decreases in association with increasing levels of exercise.
However, recent studies2,3 have found that increasing levels of physical activity are associated with reduced levels of C-reactive protein, a marker of systemic inflammation. Since elevated levels of this marker have been shown to be an important predictor of future cardiovascular events,4 these findings2,3 suggest that the association between exercise and a reduced risk of cardiovascular events may also be mediated by the antiinflammatory effects of physical activity.
4 ReferencesLuca Mascitelli, M.D.
Casa di Cura Città di Udine, 33110 Udine, Italy
lumasci@libero.it Francesca Pezzetta, M.D.
Ospedale S. Michele, 33013 Gemona del Friuli, Italy1
Tall AR . Exercise to reduce cardiovascular risk -- how much is enough? N Engl J Med 2002;347:1522-1524
Full Text | Web of Science | Medline2
Abramson JL ,Vaccarino V . Relation between physical activity and inflammation among apparently healthy middle-aged and older US adults. Arch Intern Med 2002;162:1286-1292
CrossRef | Web of Science | Medline3
Ford ES . Does exercise reduce inflammation? Physical activity and C-reactive protein among U.S. adults. Epidemiology 2002;13:561-568
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Ridker PM ,Rifai N ,Rose L ,Buring JE ,Cook NR . Comparison of C-reactive protein and low-density lipoprotein cholesterol levels in the prediction of first cardiovascular events. N Engl J Med 2002;347:1557-1565
Full Text | Web of Science | Medline
Author/Editor Response
In response to Drs. Mascitelli and Pezzetta: We agree that some of the effects of exercise training in reducing cardiovascular risk may be mediated through modulation of C-reactive protein levels. This idea would be consistent with our previous observations and those of Church et al.,1 who found an inverse association between C-reactive protein and fitness levels.
In response to Dr. Sharma: We agree that changes in total body fat or fat distribution may well play an important part in the improved lipid profile that we observed in response to the high-amount exercise-training intervention, and we are examining that hypothesis now.
Dr. Schmidt-Trucksäss alludes to our previously published report, which provides a detailed description of our methods and some preliminary results.2 In that preliminary report, the dropout rate was 16 percent in the low-amount–moderate-intensity group, 52 percent in the low-amount–vigorous-intensity group, and 20 percent in the high-amount–vigorous-intensity group. By comparing the dropout rates in the low-amount groups only, one might conclude that vigorous exercise leads to a higher dropout rate. Yet when all three exercise groups are examined together, it appears that there are other factors promoting dropout, since the rate in the low-amount–moderate-intensity group was nearly identical to that in the high-amount–high-intensity group. Overall, we believe that the data we present in the current report are too preliminary to make any firm statements regarding specific aspects of the exercise prescription that might lead to differences in adherence.
2 ReferencesCris A. Slentz, Ph.D.
William E. Kraus, M.D.
Duke University Medical Center, Durham, NC 27710
william.kraus@duke. edu 1
Church TS ,Barlow CE ,Earnest CP ,Kampert JB ,Priest EL ,Blair SN . Associations between cardiorespiratory fitness and C-reactive protein in men. Arterioscler Thromb Vasc Biol 2002;22:1869-1876
CrossRef | Web of Science | Medline2
Kraus WE ,Torgan CE ,Duscha BD , et al. Studies of a Targeted Risk Reduction Intervention through Defined Exercise (STRRIDE). Med Sci Sports Exerc 2001;33:1774-1784
CrossRef | Web of Science | Medline
Author/Editor Response
I agree that an exercise-related decrease in the C-reactive protein level could represent an antiinflammatory effect of exercise. However, an alternative explanation is that exercise improves various aspects of the metabolic syndrome, such as obesity, hypertriglyceridemia, low high-density lipoprotein levels, and abnormal glucose metabolism. C-reactive protein levels are highly correlated with the metabolic syndrome and increase in parallel with an increase in the number of metabolic-syndrome components that are present in a given person.1 Moreover, although C-reactive protein provides important incremental information about the risk of cardiovascular events, beyond the information provided by components of the metabolic syndrome, the latter appear to have a much larger overall effect on the risk of cardiovascular events.1
1 ReferencesAlan R. Tall, M.B., B.S.
Columbia University, New York, NY 10032
art1@columbia.edu 1
Ridker PM ,Buring JE ,Cook NR ,Rifai N . C-reactive protein, the metabolic syndrome, and risk of incident cardiovascular events: an 8-year follow-up of 14 719 initially healthy American women. Circulation 2003;107:391-397
CrossRef | Web of Science | Medline
- Citing Articles (5)
Citing Articles
1
Wei Guo, Hiroaki Kawano, Lianhua Piao, Nana Itoh, Koichi Node, Takeshi Sato. (2011) Effects of Aerobic Exercise on Lipid Profiles and High Molecular Weight Adiponectin in Japanese Workers. Internal Medicine 50:5, 389-395
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Tomas G. Neilan, Malissa J. Wood. (2009) Endurance Exercise and the Heart: Multiple Benefits but Many Unanswered Questions. Journal of the American Society of Echocardiography 22:7, 810-813
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A. Stergioulas, A. Tripolitsioti, A. Nicolaou. (2008) The Effects of a Classic Spartathlon Race on Lipids and Prostanoids in Endurance Male Athletes. Pakistan Journal of Biological Sciences 11:17, 2139-2143
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D. J. Becker, R. Y. Gordon, P. B. Morris, J. Yorko, Y. J. Gordon, M. Li, N. Iqbal. (2008) Simvastatin vs Therapeutic Lifestyle Changes and Supplements: Randomized Primary Prevention Trial. Mayo Clinic Proceedings 83:7, 758-764
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C. de Teresa Galván, M.aC. Vargas Corzo, C. Adamuz Ruiz. (2005) Corazón y ejercicio físico. Medicine - Programa de Formación Médica Continuada Acreditado 9:44, 2895-2899
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