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I meet people every week who are surprised and upset to find their cholesterol levels did not go down after they started an exercise program.  This failure to lower cholesterol is even more astonishing when they hear claims from exercise enthusiasts that people who run marathons never have a heart attack � even though the cemeteries are filled with long distance runners who have died from this disease.  The famous runner and author of The Complete Book of Running, Jim Fixx, is a telling example of a man who made this claim, yet met his end in 1984 from a heart attack at age 56.  His arteries were plugged solid with atherosclerosis.

The truth is: physical activity and fitness will reduce your risk of cardiovascular disease (strokes and heart attacks).  But the benefits fall far short of immunity and one reason may be that exercise shows no benefit on two of the most important risk factors for heart disease -- total and LDL cholesterol.

The November 7, 2002 issue of the New England Journal of Medicine published the latest research showing no change in total or LDL cholesterol with exercise.¹ However, there were some small changes in other less important risk factors.  Of the risk factors commonly measured, triglycerides decreased with all levels of exercise by 20 to 60 mg/dl, and HDL increased by 4.8 mg/dl only with a large amount of high intensity exercise (equivalent to 20 miles a week of jogging).  The subjects studied were overweight men and women, who were asked to eat enough during the study so they did not lose weight.  Even without weight loss they showed these improvements in triglycerides and HDL levels, which are important.

However, a change to a low-fat diet has profound effects on total cholesterol and LDL cholesterol, ultimately lowering your risk for cardiovascular disease.  In addition, a healthy diet has a huge impact on reducing the second leading cause of death, cancer � as well as improving most other aspects of health from halitosis to hemorrhoids (See McDougall Newsletters from January to November 2002). When I am asked to compare the impact of diet and exercise on health, I give diet an 80% rating and exercise 20% (assuming bad habits like smoking are not in the evaluation).

Exercise has clear health benefits in addition to those mentioned above, like losing weight, lowering blood pressure, improving mood, strengthening bone, making appetite more appropriate, building muscles, improving insulin sensitivity, and lowering blood sugars.  Therefore, do not discount its importance because of the lack of cholesterol-lowering effects.  However, most people who exercise are also interested in gaining longevity and excellent health.  They need to understand that exercise is only one part of the equation for excellent health and that diet cannot be ignored.²   Furthermore, I think it is important for people who plan to start an exercise program to get their diet fixed first.

Starting an intensive exercise program while in poor health could be a prescription for trouble � even the possibility of precipitating a heart attack with the intense exercise.^4-5  This tragedy can occur because heavy exercise may cause the disruption of a volatile plaque in one of the heart arteries, resulting in complete closure of the artery � and death of the heart muscle (a heart attack).⁶  Eating a healthy diet for a period of time before the intense exercise will help stabilize the plaque and prevent its rupture (See the McDougall Program for a Healthy Heart book.)

I encourage you to start a regular exercise program, but start it slowly and build your exercise up at a comfortable pace.  You can usually tell if you are overexerting when you have difficulty talking at the same time you exercise.  Along with your exercise, start a low-fat, pure vegetarian diet now and you will be on the road to excellent health.

References:

1)  Kraus WE.  Effects of the amount and intensity of exercise on plasma lipoproteins.  N Engl J Med. 2002 Nov 7;347(19):1483-92.

2)  Paterick TE.  Endothelial function and cardiovascular prevention: role of blood lipids, exercise, and other risk factors.  Cardiol Rev. 2001 Sep-Oct;9(5):282-6.

4  Mittleman MA, Maclure M, Tofler GH, Sherwood JB, Goldberg RJ, Muller JE. Triggering of acute myocardial infarction by heavy physical exertion -- protection against triggering by regular exertion. N Engl J Med 1993;329:1677-1683.

5)  Willich SN, Lewis M, Lowel H, Arntz H-R, Schubert F, Schroder R. Physical exertion as a trigger of acute myocardial infarction. N Engl J Med 1993;329:1684-1690.

6)  Curfman GD. Is exercise beneficial -- or hazardous -- to your heart? N Engl J Med 1993;329:1730-1731.

2002 John McDougall All Rights Reserved