I cant count the number of times I have heard stories of regular people being asked not to exercise or strain themselves for risk of aggravating their problems. The problems could range from high blood pressure to more serious ailments caused by chemical and other imbalances. In all these cases, there are doctors who have advised patients to take it easy. In any case it is extremely hard to negate medical advice and when offered it becomes virtually impossible to overcome the mental hurdle of motivating yourself to actually do something. Sometimes these opinions come in more innocuous ways such as running will lead to damaged knees.
In a study conducted by the Osteoarthritis Initiative, over 2500 patients were studied from ages ranging from 18 – 50 years for over 4 years. The cohort were asked if they had run at any point in time in their lives and their bodies then studied for injuries to their knees including whether they had ever had knee replacement. The people who had run reported a 22.8 percent risk of symptomatic osteoarthritis versus a 29.8 percent risk for those who had not run. This meant that those who had not engaged in what is perceived as a high impact trauma causing activity actually reported a higher risk of injury.
Research studies like these are focused on the co-relation between a specific activity, running for example, and the outcome, injury or otherwise. This is necessary to determine the impact of the specific activity. I on the other hand clearly see the benefits of engaging in and living a healthful life one in which you are eating clean, exercising and building mental strength through some form of meditation. When you run for example, it is virtually impossible to just run and not take care of how you eat, sleep etc. Its just too much hard work and your mind and body immediately wants to conserve the benefits of this exertion. This puts you into positive loop giving you mental confidence, will, drive and motivation and also the ability to say no to the cheesecake. OK, not everyday but most days! The benefits of this positive loop will in all probability out weigh the risks of strain or injury caused by most forms of exercises.
PS: Please note that I am not a Doctor and my opinion is based on my limited understanding of health. If your Doctor has indeed advised you to not exercise, please take the advice seriously or consult an expert before engaging in any form of serious exercise.