DEAR DOCTOR K: You often recommend exercising for 30 minutes a day, most days of the week. That target intimidates me. Is it worth it for me to exercise less, say 15 minutes, three days a week? Or is there no benefit unless I commit to the full 150 minutes per week?

DEAR READER: I’m glad you asked that question, because there are a lot of people who are daunted by the thought of exercising that much – and therefore don’t do it at all. It is true that I do advise 150 minutes of moderate-intensity activity each week. But two recent studies, while not changing my view that 150 minutes is best, show that less than this still brings benefits.

First, let’s establish what we know: Regular exercise protects you against many major diseases. That includes heart disease, diabetes, osteoporosis, depression and even some cancers. In fact, there are no medicines yet invented that can protect you against these diseases as well as regular exercise.

But how much exercise?

One research team analyzed studies of physical activity in over 800,000 people. The more time that people were sitting down each day, the greater their risk of heart disease and cancer. The people who spent the most time sitting down, compared to those who spent the least time, had a 24 percent higher risk of dying prematurely. And they had a 90 percent greater risk of getting diabetes.

Another research team in Denmark compared death rates in regular joggers, light joggers and non-joggers. Light joggers were those who jogged at a slow or moderate pace just two or three times a week, for 60 to 145 minutes. Not surprisingly, the light joggers had much lower death rates than the non-joggers. But surprisingly, the light joggers also had somewhat lower death rates than the regular joggers.

Exercise is on a spectrum. On one end is no activity; on the other end is 150 minutes or more of exercise per week. In between there is a continuum. You benefit from any level of activity on that continuum.