Lack of exercise is a definite risk factor in the development of cardiovascular disease, diabetes, obesity, some cancers and many other diseases. This has been a definite finding in most studies.
With both men and women, there is a 20 to 35 percent of relative risk reduction to all causes of death, including lifestyle diseases for those who do the maximum physical activity. Wharburton and colleagues who did a review of many studies in 2006 note those physically inactive middle-aged women are at a 52 percent increase to all causes of mortality. It appears that there is a linear relationship with increased physical activity and improved health status.
Moderate exercise is what is recommended by most experts. Exercise can be regarded as either aerobic or muscle-strengthening. Aerobic exercise uses our heart and lungs and includes brisk walking, running, cycling and swimming. Push-ups, sit-ups, weight training etc are the other type. Generally recommended exercise is 30 minutes of moderate exercise five days a week and weight training activity for 15 minutes on two days a week. How do you know we are doing moderate activity? We should be able to appreciate our heartbeats and will be sweating lightly, but will be able to carry on a normal conversation. More vigorous exercise will have us panting more, and not able to speak other than one or two words at a time.
People planning regular physical activity at middle age should probably have a medical check-up before starting.
One important way in which exercise works is by reducing the incidence of obesity. Excess weight due to accumulation of fat occurs due to taking in more calories as food than we expend by activity. Obviously, exercising expends calories and helps in weight loss. As we have seen, obesity is a risk factor for many diseases, most importantly, Diabetes.
Aerobic exercise increases the efficiency of carbohydrate metabolism. Over time, the muscles become more efficient at utilizing glucose to create energy. This reduces blood sugar. The blood glucose becomes more easily controlled by the insulin that is secreted by the body. This greater sensitivity to the action of insulin is an important factor in preventing Diabetes. Pre-diabetes, a precursor state of diabetes is characterised by relatively high blood sugar in spite of high circulating levels of insulin. This slowly tires the islet cells in the pancreas and later insulin deficiency occurs. Regular exercise has a preventive effect on the whole process. It is also a treatment for established diabetes, reducing its severity and decreasing the amount of insulin and medicines used to control the disease.
Muscle building exercise is also important. It has some unknown effect on diabetes control. Studies have shown that combining aerobic and muscle building resistance exercises is better at preventing diabetes than either alone. Muscle uses more energy at rest than fat. So more muscle means more energy expended. The increased muscle mass also acts as an endocrine organ, mediating many benefits, while abdominal fat secretes chemicals that cause many unwanted effects.
Exercise has many effects on fat metabolism. It very reliably increases the level of HDL in the blood. HDL, as we know, promotes the movement of atherogenic cholesterol into the liver. It also decreases the level of triglycerides in the blood. There is a moderate effect on the LDL levels also, bringing it down to a healthier level.
Above all, exercise burns calories and makes you less fat. This is obvious. Less fat means less intra abdominal and visceral fat. That is one important risk factor less that contributes to your ill-health.
Apart from effects on physical health, there are other benefits also. Scientists have found that regular physical activity is a potent treatment for mild to moderate depression. When you exercise, an especially after a duration of any aerobic exercise, the brain releases ‘endorphins’. Endorphins are naturally secreted opiods, similar to morphine and heroin. They create ‘the runner’s high’- a pleasant feeling of exhilaration and release. It also has an effect on the hypothalamus in the brain that responds to stress via the pituitary and adrenal axis. The physiologic reactivity to stress is modified in a way that damps it down. It has been shown to decrease anxiety and depression and increases self-esteem.
It was in the 1960s that rats were made to exercise regularly on treadmills. Physically they must have become fitter. We don’t know. But that was not what was studied. Researchers found that the exercised rat’s cerebral cortex became thicker. New cells were being laid down. The effect was strong in the hippocampus, which is a sort of nursery for the formation of new neurons. What is more, these ‘runner rats’ were better at learning and memory skills, like running mazes, showing that they have actually become smarter. Recently Japanese researchers at the University of Tsukuba found a possible mechanism for this puzzling effect. They found that exercise rapidly depletes the stores of glycogen, a stored form of glucose that is present in astrocytes in the brain. Astrocytes are neighbour cells to neurons. They envelope, protects and nourishes them. Regular exercise drastically increases the amount of stored glycogen in these cells as a form of super-compensation. Want to boost your smarts? Better reach for those running shoes. Or the swimming trunks – whatever.
To underline everything, Marc Hamilton, a leading figure on inactivity physiology has coined the startling phrase- ‘sitting is the new smoking’. My god! These researchers won’t even leave us to sit in peace. Many like him claim that sitting is an independent risk factor. Any prolonged sitting, as in an office does actual harm. And it is not offset by any exercise that you may do later in the day. So stand and write those reports. Increase your desk height and prop your computer on it, so that you can stand in front. Fidget. Take a walk. Do anything, but don’t sit. Shit!
Many lifestyle interventions work in ways that we cannot predict. One psychiatrist friend told me about a patient suffering from depression that was somewhat resistant to medicines. He advised him to start walking. The improvement was dramatic. He was rapidly off all drugs as his walks became longer. Then suddenly one day he was totally cured and announced that he was divorcing his wife.
The walks allowed him an excuse to be away from his nagging wife. The more he walked, the happier he became. Finally he got to the root of the problem and was fully cured.