Food gives us nutrition for the body to grow; and it gives us energy to work and play. But it can also wreak havoc, if you don't keep a watch on what you eat.
As we grow older, there should be increasing regulation of the food that we eat. Avoid meat, especially red meat. Fish is good, but avoid the fried form. That should take care of most health issues. It's not easy as it sounds.We are talking of nearly monastic diet; food that has minimum content of fat, salt, sugar and oil.
If one tries this out, with some determination, the effect on health can easily and immediately be seen. What works best is not complete ban on these villainous food additives, but regulation. Avoid them most of the time, but indulge once in a while. It'sn't easy; but with some steely resolve it's possible.
To be healthy, there is no need to go to a gym and employ a physical trainer. Just make sure you do enough of physical activity - anything from getting up from chair and walking around, to climbing stairs, to washing clothes to mopping the floor, to going on a long walk. Additionally, do some 20 minutes of breathing and stretching exercises daily. Rather than vigorously exercising for long hours once in a while, it's better to exercise in short spells more frequently.
Here's an article from New Scientist that says in order to lose weight one mustn't skip food, but cut down on fat.