Enjoy immediate gains by developing a well-rounded program, performing the exercises with good form, and being consistent.

Regular physical activity promotes general good health, prevents chronic disease, and helps you live a longer and healthier life. For many of us, the exercise prescription comes in the form of walking, jogging, treadmill work, or other "aerobic" activities that get your heart pumping.

Use of diagnostic imaging has risen sharply since the 1990s, exposing some people to "high" or "very high" doses of radiation, according to a report in the Journal of the American Medical Association. Researchers studied records of diagnostic scans conducted from 1996 to 2010. Use of ultrasound grew by 4% annually. CT use grew by 8%, MRI by 10%, and PET by 57%.

Because CT and PET scans involve exposure to radiation, their increased use raises a potential safety issue. A CT scan of the chest delivers an amount of radiation equivalent to that of 200 chest x-rays. That means after just 10 chest CT scans, a person can reach his or her safe lifetime limit of radiation exposure, according to the American College
of Radiology.

In the journals

It's never too late to quit smoking

People who quit smoking late in life still benefit, according to a study in the Archives of Internal Medicine. Researchers pooled results from multiple studies that measured the increased risk of death in smokers 60 and older. Data from 17 studies conducted in seven countries showed that older smokers are 83% more likely to die than people who never smoked. This risk fell to 34% in people who quit. In short, kicking the habit still leaves smokers at a higher risk, but it is significantly lower than in they continued smoking.

The reduced risk gained by quitting smoking was similar in men and women. And even in people who quit in their 80s, risk dropped by 24% compared with people who had never smoked. "Even older people who smoked for a lifetime without negative health consequences should be encouraged and supported to quit," the scientists noted.

Q. I often fly on business from Chicago to Europe. Do you have any tips for managing jet lag?

A. Jet lag is common when flying long distance across several time zones. For every time zone you cross, it takes about a day for your body to adjust. There is no proven solution for jet lag, but you may be able to minimize its effects.

Daily physical activity reduces a woman's chances of developing breast cancer. Women who work out between 10 and 19 hours a week have a breast cancer risk about 30% lower than that of inactive women.

Losing weight sometimes takes experimentation. If you give a diet your best shot and it doesn't work long term, maybe it wasn't the right one for you, your metabolism, or your situation. Genes, family, your environment — even your friends — influence how, why, what, and how much you eat, so don't get too discouraged or beat yourself up because a diet that "worked for everybody" didn't pay off for you. Try another, keeping in mind that almost any diet will help you shed pounds — at least for a short time.

Here's a look at three common diet approaches.

Q. If you exercise daily (and sweat), can you have more than the daily recommended limit of sodium?

A. The simple answer is "Yes," but it really depends on how much you exercise and sweat, and how much sodium already is in your diet. Sodium in our diet comes largely from salt (sodium chloride). You need to have enough sodium in your diet each day to keep up with the sodium you lose in your urine and sweat. It is recommended that most adults ages 50 or younger have no more than 2,300 milligrams (mg) per day of sodium. For people 51 or older, for African Americans of any age, and for people with diabetes, high blood pressure, or kidney disease, the recommended level is 1,500 mg per day.

Research connects the drinks to higher heart risks.

You may think you're doing yourself a favor by opting for an ice-cold diet soda every afternoon instead of the sugar-sweetened version and all the calories that go with it. Not so fast: recent research suggests that diet sodas may also lead to problems.

In a study published in the Journal of General Internal Medicine, researchers found that people who drank diet sodas daily were at a higher risk for vascular events, such as heart attack and stroke, compared with those who drank fewer diet sodas or even those who drank regular sugar-sweetened sodas.

When it comes to the challenge of sticking to your daily medication routine, a little encouragement can go a long way.

A study published in Archives of Internal Medicine found that simple steps such as phone calls and rewards can help people take their medications as prescribed.