TAKE IT EASY AS YOU GET OLDER? NOT IF YOU WANT TO LIVE LONGER!

A team of evolutionary biologists and biomedical researchers lay out evolutionary and biomedical evidence showing that humans, who evolved to live many decades after they stopped reproducing, also evolved to be relatively active in their later years. The researchers say that physical activity later in life shifts energy away from processes that can compromise health and toward mechanisms in the body that extend it. They hypothesize that humans evolved to remain physically active as they age -- and in doing so to allocate energy to physiological processes that slow the body's gradual deterioration over the years. This guards against chronic illnesses such as cardiovascular disease, type 2 diabetes, and even some cancers.

Harvard researchers say that physical activity later in life shifts energy away from processes that can compromise health and toward mechanisms in the body that extend it. They hypothesize that humans evolved to remain physically active as they age -- and in doing so to allocate energy to physiological processes that slow the body's gradual deterioration over the years. This guards against chronic illnesses such as cardiovascular disease, type 2 diabetes, and even some cancers.

It's a widespread idea in Western societies that as we get older, it's normal to slow down, do less, and retire. However, this message is the reverse: As we get older, it becomes even more important to stay physically active.

This research is the first detailed evolutionary explanation for why lack of physical activity as humans age increases disease risk and reduces longevity.

The study uses humans' ape cousins as a jumping off point. The researchers point out that apes, which usually live only about 35 to 40 years in the wild and rarely survive past menopause, are considerably less active than most humans, suggesting that there was selection in human evolution not just to live longer but also to be more physically active.

They hypothesized that our "hunter-gatherer", ancestors averaged about 135 minutes of moderate to vigorous physical activity per day (about six to ten times more than average American). They believe that this may be one of the keys to why (those who survived childhood) tended to live roughly seven decades. Fossil evidence indicates that these extended lifespans were common by 40,000 years ago, contrary to the belief that human lifespans until recently were short.

The team emphasized that the key health benefit of physical activity is to extend the human "healthspan", which is defined as the years of life spent in good health.

Researchers examined two pathways by which lifelong physical activity reallocates energy to improve health. The first involves dealing excess energy away from potentially harmful mechanisms, like excess fat storage. The team also identified how physical activity allocates energy to repair and maintain biological processes. The paper shows that besides burning calories, physical activity is physiologically stressful, causing damage to the body at the cellular level. The body's response to this damage is essentially to build back stronger.

This includes repairing tears in muscle fibers, repairing cartilage damage, and healing microfractures. The response also causes the release of exercise-related antioxidants and anti-inflammatory compounds, and enhances blood flow. In the absence of physical activity, these responses are activated less frequently. The cellular and DNA repair processes have been shown to lower the risk of diabetes, obesity, cancer, osteoporosis, Alzheimer's, and depression.

The key take-home point is that because we evolved to be active throughout our lives, our bodies need physical activity to age well. In the past, daily physical activity was necessary in order to survive, but today we have to choose to exercise, to perform voluntary physical activity for the sake of health and fitness.