The body of the article has some great suggestions, but the headline is clickbait. Lots of low-intensity activity is great for health of course. But if you only have 3 hours per week to exercise, spending those 3 hours at the gym doing high-intensity exercise, is far better than just taking a leisurely stroll. For people with busy lives, going to the gym provides the best ROI for your time. For an obvious illustration of this, you can see the research done on HIIT vs low-intensity exercises:

http://time.com/4893161/hiit-high-intensity-interval-trainin...