William RevilleScience of Life
We would all like to live a healthy physical lifestyle. Such a lifestyle mainly involves two activities – exercise and eating. We are continually bombarded in the media with advice on exercise and healthy eating and the whole thing is made to seem complex and difficult to negotiate. However, the recipe for a healthy life is well established and easy to understand. A little discipline is required to get healthy habits established initially but the consequent feelings of well-being then make it easy to maintain the healthy habits.
Viewed as machines our bodies are unusual in that they grow stronger with use and weaker if underused – your muscles grow bigger when regularly exercised and waste away when not used. Exercise is fueled by energy derived from the food we eat and if we take little exercise we retain these calories and grow fat.
The three main types of exercise are aerobic exercise, general moving-about exercise and resistance exercise. Aerobic exercises, such as brisk walking and jogging, exercise the heart and lungs. General movement exercises include all our ordinary everyday activities – walking around the house, setting the dinner table, washing the dishes, etc. Resistance exercise basically involves lifting weights.
There is copious evidence that regular aerobic exercise is good for your health, significantly lowering the probability that you will contract heart disease, diabetes, obesity and high blood pressure and also enhancing your sense of psychological well-being. But a very important recent finding is that general moving-about exercise is much more important than we previously thought.
The average person sleeps one third of the time – eight hours per day – but we tend to forget that the average person with an office job also sits for another eight hours per day. In other words, many people are inactive two thirds of the time. We all need about eight hours sleep every day but there is no need for us to sit for another eight hours and we now know that such all-day sitting has a corrosive effect on our health and also reduces the benefits derived from vigorous aerobic exercise. A recent study reported in Time magazine (http://time.com/sitting/) showed that, regardless of how much aerobic exercise they take, people who sit for more hours of the day have a 25% greater risk of developing colon cancer, 32% higher risk of endometrial cancer and a 21% higher risk of lung cancer. Another study showed that the more hours spent sitting the less the fitness benefits derived from aerobic exercise.
So, what do you do if you have a desk-bound office job? The simple answer is to stand up every 20 minutes or so and take a walk down the corridor before returning to your desk. Also take a 15 minute walk in the open air after lunch. A more extreme solution is to swap your sit-down desk for a workstation at which you stand rather than sit. You could even buy a specialised standing workstation that incorporates a treadmill. But the simplest and probably the best solution is to break up your sitting day with regular short strolls down the corridor.
You burn off many more calories standing up than sitting down. You may only burn 300 calories sitting down for eight hours but if you are on your feet behind a fast food counter serving customers for eight hours, for example, you will burn about 1,400 calories. So, a regime of punctuating your sitting day with regular short strolls also helps to keep the weight down.
And now to active aerobic exercise, the kind of exercise that works up a sweat – brisk walking, jogging, running, swimming, cycling, etc. I listed the health benefits of aerobic exercise earlier but how much exercise do you need to achieve these benefits? I will quote the figures for walking and for running. The average person will receive optimum health benefits if he/she, five days per week, walks 6.5 km in 70 minutes or runs 4.8 km in 38 minutes. If you are not used to walking/running you will have to gradually work up to these targets over say eight weeks. You can of course go on to walk/run further and faster each day than the targets I quoted. This will make you aerobically fitter but will not produce any extra health benefits beyond those achieved by the quoted targets.
Resistance exercises strengthen muscles and bones and are particularly important for elderly people whose muscles and bones tend to weaken with age. Regular resistance exercising will ameliorate the symptoms of arthritis, diabetes, osteoporosis, obesity and back pain. It will also restore balance and reduce falls. Stretching exercises are also particularly important for older people. Lack of flexibility can be a major problem with elderly people – difficulty in bending down, in reaching up, in maintaining a straight posture, in holding the head erect and so on. A simple daily routine of light weight training and stretching will keep you toned and supple.
And finally to a subject on which staggering amounts of confusing and even self-contradictory information is published every day – what constitutes a healthy diet? This is not a complicated matter at all. After much reading and thinking about this matter I have concluded that I agree with food writer Michael Pollan’s advice that the average person, who is not suffering from specific diagnosed medical problems, will derive maximum sustenance from food by eating a wide variety of whole food, mainly plants, in moderation. There is no need to demonise any food and by eating a wide variety of food you ensure that you don't miss out on anything important. You should generally avoid, or greatly minimize, processed food, but if you occasionally eat a pizza it is no big deal.
So, in summary, the recipe for a healthy physical lifestyle is do the recommended aerobic exercise every second day, do light weight training and stretching exercises every second other day and eat a wide variety of whole foods, mainly plants, in moderation every day.
*William Reville is an Emeritus Professor of Biochemistry at UCC http://understandingscience.ucc.ie