Sitting for a long time is bad for you, so if you use the computer a lot build yourself a standing desk.
I used to run marathons. Doing that teaches you a lot. One is the hard/easy principle, don't exercise the same muscle groups hard every day. The other is that is takes an enormous amount of exercise to run off a high carbohydrate meal. It's simply not sensible to try and control your weight by exercise. Counting calories is not a sensible approach to weight control either.
There are excellent reasons to exercise, and to keep exercising strenuously all your life. You need strong lung capacity, the ability to breath deeply and process lots of air quickly. You need strong bones, and the easy way to get strong bones is to lift weights. You need strong muscles, that can do a lot of work, and you do that by doing enjoyable things, with other people, like playing sport, walking, dancing or Tai Chi.
In "The triumphs of Experience", George Vaillant tells us that the evidence that people who exercise are more healthy is weak. On the other hand, the evidence that people who are healthy love to exercise and play games and strive to do their best. He describes physical and mental health as the "horse" that makes exercise and striving and effort possible.
You Don't Need to be Feeble in Your Old Age
Modern lifestyles create lifestyle diseases we can avoid with a little understanding and care. High blood pressure, heart attacks, cancer and diabetes for instance were unknown in many "primitive" societies. This was reported by Dr Weston Price in the 1930's, and confirmed by many other physicians, in societies as diverse as the Inuit, the Maasai, and the North American Indian. We don't really understand why we're causing this problem for ourselves. It's clearly something to do with our "lifestyle" which is a catch-all for "lots of things" and "we don't know".
We can pretty clearly see that wrong dietary information is part of it. The Inuit, the Maasai, and the North American Indian ate lots of red meat, ate large amounts of animal fat, had little or no sugar and very few vegetables. How different from us, yet free of disease, even in old age.
There's quite a lot of literature and research into the importance of exercise for older people. Tai Chi in rest homes and weight training for seniors are examples. Tai Chi encourages both strength and flexibility, and weight training is a way to make measurable gains quite quickly. Listen to what your own body is telling you. Fifteen minutes quiet meditation at the beginning of the day can help to clear the mind and reinforce what's really important.
The body is designed to be used.
I've seen in athletics, in Tai Chi, and in ballroom dancing, that people who are active in middle age, and who get to age 60 in good health and fitness, are likely to maintain that fitness until very close to the time of their death. People who live well, can be strongly involved with their families and the community, and actively contributing until the end of their lives.
Dr Patterson Stark recommends weight training. He has a formula which encourages more repetitions with a lighter weight, rather than three repetitions with a heavier weight that most trainers use. That is in line with marathon training principles, and encourages the sort of strength gymnasts have, rather than the sort of strength body builders aim for. Find out maximum weight you can lift once. Use 60% (or less) of that weight for training. Move the weight SLOWLY, always under control, both up and down. Keep the muscles under tension and exercise to failure. (Until you can move the weigh any more.) Try to hold it there as long as you can. Then recover.
Shift to another muscle group with a different slow movement exercise. Exercise to failure.
Move on to something different, perhaps a punch bag, work quickly until you are very tired. By now you should be really puffing.
Don't do these exercises again for SEVEN days. You must allow muscles that have been tested to failure to fully recover. It's the recovery that makes the muscle strong again. You damaged the muscle, let if heal itself fully.
Get outside and walk, or run or play games.
Our bodies are designed to spend time outdoors every day, and to walk considerable distances and to carry loads. We should be able to easily walk up stairs, and able to stand a lot, even if you are over 70 years old. Unless you are unfortunate, being healthy in old age is a choice you can make.
That should be your expectation for yourself. If you are strong, a strength developed by good exercise habits, good diet and an active working and social life, even if a cancer of some other problem comes along, your ability to deal with it is enhanced.
Whole Body Training Suggestions
Here is an example of my "Whole Body Training" concept. Three days of completely different exercises that use your whole body and require very little in the way of equipment.
The body has to be nourished.
Since health is our topic I don't expect that smoking and excessive alcohol use are part of your life. If they are you know what to do.
What you eat is important of course, but you nourish your body in other ways too. What do you choose to do with your time? How much physical activity do you build into each day? What do you work at, and does that bring you joy and satisfaction? How many friends do you have, and how good is your connection with them? How much time do you spend outdoors and with nature? In particular do you get time in the sunshine every day? Spend some time in the garden. How much quality sleep are you getting? Day-time naps are good. Get up when you wake up, and start work. Go to bed when you are tired.
All of these activities nourish your body, and help to keep you active and involved and happy. It's not normal to be sick.
Your Example for your Grand Children: We are passing on to our grand children, a world that we have helped make more dangerous and less hospitable to human existence. Who are we to give them advice? What we can do is be an example, a living testimony as to how they might try to deal with problems and relate to other people. Nothing you can say is enough. Who are you? That's what they will learn and remember from watching you.
Your Health can be Improved
The general principle that guarantees improvement is to evaluate your health, write down what your evaluation is. Now choose something you want to improve. Make a choice to change ONE thing that you hope will give you a better result. Write that decision down. Do what you have decided. Over a reasonable time record the result. Better/Not better? Can you measure or estimate the change? Write it down.
Carolyn and myself recommend dancing and walking. Both activities are best done in a group setting; join a club. Carolyn is very involved in T'ai Chi Ch'uan, or Qigong. The people involved in all these activities are the sort of people who will help you build your life and your friendships.
Charles Eugster. Overweight and in declining health at 87. Fit and healthy and winning gold medals at 93.
These "official" exercise guides, tend to be a disappointment.
The Center for Disease Control and Prevention (USA) also makes recommendations about exercise for everyone.
The American Heart Association has recently published, A New Standard for Exercise: It is Time to Move it to Make it a High-Level Priority.