A few days after writing my previous post entitled “Detraining (or what happens when we stop training)”, my good friend Brenda Barrett e-mailed me and asked me the question that has become the title of this new post: what happens when you don’t start training?

I thought this is an excellent question, so I decided to try and provide Brenda (and everyone else reading this blog) with an answer. I must admit that I have been so focused on sports performance throughout my career as a physiologist, that I am not an expert in the relevant areas of exercise physiology that best answer the question above. Therefore, I have decided to borrow a text from my good friend and colleague Prof. John Hawley, Head of the Exercise Metabolism Research Group at RMIT University in Melbourne, whom, in collaboration with Profesor John O. Holloszy of the Division of Geriatrics and Gerontology at Washington University in St. Louis wrote and excellent paper entitled “Exercise: it’s the real thing!” Nutrition Reviews Vol. 67 (3):172-178, 2009.

So here it is, my answer to Brenda’s question:

“While physical inactivity has emerged as a major risk factor implicated in many “lifestyle” disorders, it has long been known that regular physical activity (i.e., exercise training), in addition to preventing obesity, induces a multitude of favorable adaptations within skeletal muscle and the cardio-respiratory system, which have positive outcomes for both the prevention and treatment of almost all metabolic disease states. However, between 50% and 70% of American adults do not get enough physical activity to provide health benefits and 25% of adults are not active at all in their leisure time. Indeed, most individuals in industrialized nations have chosen to ignore the minimum physical activity guidelines recommended by health organizations such as the American College of Sports Medicine and will suffer the consequences.”
“Regular, vigorous exercise has been necessary for survival throughout evolution. It is only during the past 50 years that it has become possible for people to go through life with minimal physical activity. We are not genetically adapted for the sedentary lifestyle that has become so prevalent in developed nations. Lack of exercise is, therefore, abnormal and also unhealthy, leading to obesity, insulin resistance, type 2 diabetes, and increased risk of developing atherosclerosis and cancer. A sedentary life is now so prevalent that it has become common to refer to exercise as having “healthy benefits”, even though the exercise-trained state is the biologically normal condition. It is a lack of exercise that is abnormal and carries health risks.”

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