One of the most famous of the Plague Regressers, as I call them is Dr. Esselstyn. He has long argued that he can regress plaque in his patients without without exercise. In other words, his experiece is that diet is more important that exercise when it comes to reversing atherosclerosis. And the other Plaque Regressers, Drs. Gould and Davis, also do not have much of an emphasis on exericse in my opinion. Their book have considerable information on diet and little on exericse and so the conclusion seems obvious to the reader. Furthermore, there are many athletes and men in fantastic shape that drop dead from a heart attack and with ample plaque in their veins, so exercise is only so protective.
But what does this really prove? Perhaps you can regress plaque without exercise, but why not turbocharge your plaque reversal? As I'll show below, the arterial benefits of exercise are overwhelming. It's not something to put on the backburner while you're cleaning up your diet: it's something to do right now to radically improve your cardiovascular health.
In fact, I believe that it will be much more difficult for the typical modern, urban dweller to control his atherosclerosis without exercise. Yes, diet is #1, but in my opinion, it generally needs its partner, exercise, in order to reach the finish line for many reasons I will outline below And, as an added benefit, exercise will protect and boost your sex life in dozens of key ways, something I document in my page on Sex and Exercise in considerable detail.
So let's go over the Eight Compelling Reasons that Exercise Can Help Regress Atheroslcerosis (Arterial Plaque) from the research:
1. Increased Nitric Oxide. Nitric oxide is a potent anti-inflammatory, lowers blood pressure and, as we all know, improves erectile strength. Nitric oxide is so powerful that it is considered anti-atheroslcerotic. This creates a vicious circle in some men, because, as they form arterial plaque on a Western Diet, their nitric oxide is lowered, which leads to more plaque and so on. Exercise, though, can help break one out of that pattern, because it powerfully raises baseline nitric oxide and leads to increased nitric oxide activation. I document the studies that discuss this in my page on Exercise and Nitric Oxide.
NOTES: One study showed that intense exercise did not lead to increased nitric oxide levels, because it created a heavy oxidative (free radical) load. Nor did mild exercise, because it just did not stimulate nitric oxide sufficiently. However, moderate exercise had a powerful nitric oxide-boosting effect and thus may be the best way to boost NO levels post-exericse. Again, see the page above for more information. NOTE: My favorite form of exericse is weight lifiting. However, I have to admit that it may not be the best exercise for arteries. In fact, there is some evidence that a certain percentage of men experience "stunned", hardened arteries post-exercise. See my page on Weight Lifting and Your Arteries for more information. This is why I always do some cardio after lifting weights.
2. Lowered Blood Presure. Exercise has a powerful, positive effect on blood pressure and just walking alone has been shown in several studies to decrease systolic blood pressure between 10 and about 13.5 mm.  This is as powerful as many medications. High blood pressure is a huge risk factor for erectile dysfunction, stroke and atherosclerosis and so this is a no-brainer. Also, in my page on Walking and Blood Pressure, I discuss a study that found that walking actually lowered blood pressure more than running. Again, this is probably because of the factor I mentioned above in #1, where moderate exercise trumps both mild and intense exercise when it comes to nitric oxide responsiveness.
By the way, high blood pressure probably is a sign of underlying conditions that cause atherosclerosis, particularly prediabetes / Metabolic Syndrome, and also causative of atherosclerosis. Obviously, increased pressure on arterial walls can lead to slight increases in damage that accumulate over the months and years.
3. Decreased Insulin Resistance. Insulin resistance is an epidemic in America and most other modern societies. And no wonder, since it is the hallmark symptom of prediabetes or Metabolic Syndrome. Of course, insulin resistance is also a risk factor for the accelerated buildup of arterial plaque and one of the primary reasons is that it leads to an increased LDL particle count (LDL-P or, alternatively, apoB). Many studies have now shown that the higher the LDL particle count (or apoB), the greater the atherosclerotis. See my page on LDL-P Particle Count Levels for more information. Those of you that have already been diagnosed diabetic or prediabetic are likely already familiar with A1C and should be impressed with the fact that exercise has been shown in a number of studies to lower A1C by 0.5 - 1.0%. This means that exercise alone can effectively reverse prediabetes for many men.
4. Reduced Oxidation of LDL. What is the most important LDL-related factor leading to atherosclerosis? The research to date indicates that the sheer concentration of LDL particles in the blood is the most important factor. However, another important factor is how much of that LDL is oxidized. Studies show that exercise can reduce oxidized LDL in the 20 to 25% range. 
5. Increased eNOS Efficiency. Endothelial Nitric Oxide Synthase (eNOS) is the enzyme involved in your arterial nitric oxide production. Exercise upgrades its "efficiency," i.e. it will increase nitric oxide produced from this pathway. 
6. Decreased Inflammation. Many of you know that certain inflammatory markers, such as IL-6 and CRP, are predictive of atherosclerosis as well as many other chronic diseases. Several studies have shown that exercise cna decrease levels of these and other inflammatory cytokines.  NOTE: One study showed that weight lifting did not lower these markers.
7. Stabilization of Plaques. A couple of animal studies show that long term exercise stabilizes plaque. It is "unstable" plaque that is so deadly.  It can rupture, ,which then forms a "clot" that can lead to a stroke or heart attack.
8. Improvements in Lipids. We all know the standard lipid test that includes HDL, LDL and triglycerdies. These are still often on many annual physicals and you can pull these numbers here in the U.S. for around $20 to $25 at one of these inexpensive laboratories: Testosterone Labs.
a) Triglyceride Reduction. I discuss on my page How to Lower Your Triglycerides different exercising strategies that can lower baseline and post-meal triglycerides levels by about 20-25%. Exercise - and that includes weight lifting for you fellow gym rats out there - can do nice job on your triglycerides.
b) Raising HDL. Endurance exercise (cardio) now has many studies showing it improves HDL between about 5 and 20%. The study mentioned above describing how exercise reduces oxidized LDL also showed an increase in HDL of 15%.  Note that HIIT also improves HDL.
CONCLUSION: As you can see, exercise is the perfect complement to any anti-plaque diet.. A notable example of this is Nathan Pritikin who had extensive cardiovascular disease in the first part of his life and reversed it with a low fat diet and exercise. He ran from what I have read for an hour per day and died with perfect clear arteries. The coroner certified that his arteries were plaque-free. His goal was imitate some of the healthiest and long-lived cultures on the planet, such as the famed Tarahumara. The Tarahumara, who are probably the healthiest people on the planet: I cover their diet in my page on The Diet of the Tarahumara.
2) Medicine and Science in Sports and Exercise, 1998, 30(10):1496-1501, "Reduced oxidized LDL levels after a 10-month exercise program."
3) International Journal of Sports Medicine, 2005, 26(6):420-425, "Acute prolonged exercise reduces moderately oxidized LDL in healthy men"
4) Circulation, 2003, 107:3152-3158"Regular Physical Activity Improves Endothelial Function in Patients With Coronary Artery Disease by Increasing Phosphorylation of Endothelial Nitric Oxide Synthase"
5) Brain, Behavior, and Immunity, May 2006, 20(3):201 209, "Aerobic exercise, but not flexibility/resistance exercise, reduces serum IL-18, CRP, and IL-6 independent of -blockers, BMI, and psychosocial factors in older adults"
6) Med Sci Sports Exerc, 2009 Dec, 41(12):2128-35, "Long-term exercise stabilizes atherosclerotic plaque in ApoE knockout mice"