Scientific evidence for the benefits of exercise is piled deep and high. The benefits for general health, longevity, and resistance to age-related disease are greater and far more broad than anything medical science can do for you today, or is likely to be doing for you over the next decade - first generation calorie restriction mimetics included. Here is one recent example of many studies that show exercise to reduce mortality, extend healthy life, and lower the rate at which age-related degeneration sets in to boot:

Changes in Cognition and Mortality in Relation to Exercise in Late Life: A Population Based Study

On average, cognition declines with age but this average hides considerable variability, including the chance of improvement. Here, we investigate how exercise is associated with cognitive change and mortality in older people and, particularly, whether exercise might paradoxically increase the risk of dementia by allowing people to live longer.

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High exercisers (at least three times per week, at least as intense as walking) had more frequent stable or improved cognition [42.3%] over 5 years than did low/no exercisers (all other exercisers and non exercisers) [27.8%] ... People who did not exercise were also more likely to die [37.5%] versus [18.3%].

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Exercise is strongly associated with improving cognition. As the majority of mortality benefit of exercise is at the highest level of cognition, and declines as cognition declines, the net effect of exercise should be to improve cognition at the population level, even with more people living longer.

So why aren't you out there exercising already?