In the 2013 movie "About Time," 21-year-old Tim Lake decides to use newly discovered powers to travel back in time and win over the girl of his dreams. His success emboldens him to "fix" more past events, threatening the future.

As with most time-travel tales, the lesson is, "You don't get a do-over."

Well, nothing could be further from the truth when it comes to past health mistakes and your future well-being. Dr. Mike's book "This Is Your Do-Over: The 7 Secrets to Losing Weight, Living Longer, and Getting a Second Chance at the Life You Want" makes that crystal clear.

A new study, called “Reversing the Cardiac Effects of Sedentary Aging in Middle Age,” reveals that with two years of regular exercise, most out-of-shape, sedentary middle-agers can improve heart health and reduce their risk of heart failure.

The participants' routine included four to five days of activity weekly:

• One 30-minute session of high-intensity, aerobic interval training (heart rate tops 95 percent of peak rate for 4 minutes, with 3 minutes of recovery), repeated four times. Check with your doctor before you begin, then build up to it.

• One session of moderate intensity for 60 minutes — tennis, walking or biking qualify.

• One or two additional 30-minute weekly sessions of moderate intensity; you're sweaty, but you can still talk. (Try interval walking, heading for 10,000 steps.)

• Then, one or two weekly strength-training sessions on separate days, or after an aerobic session.

So take charge, and you'll be rewarded with a change in the quality and length of your future timeline.