Editor's note: John Farah is the co-author of "Let's Pick it up a Bit," a memoir and a guide to help people lead an active life. He has run more than 430 races, including 123 marathons.
(CNN) -- Pick someone you know -- anyone at all -- and ask them this simple question: "Do you work out?"
This time of year, the answer will usually be "yes."
It is in vogue to exercise and even more in vogue to run. But with New Year's resolutions quickly fading, the real question is this: How do you turn a fad into a lasting, meaningful habit and a healthy lifestyle?
It all comes down to what I like to call my "4-8-12 Fitness Rule" © -- a rule I've developed after 40 years of exercising regularly and talking with other people who do as well.
Scientific? No. Worth doing? Definitely.
To establish a minimum baseline of fitness, a person needs to exercise about four hours a week.
Four hours per week is 240 minutes. Not bad, right? That's a lot less time than most of us spend watching TV. Even better, you can break that down any way you want.
If you work out 40 minutes per day, six days a week, you got it. Or if you prefer, make it 60 minutes a day, four times a week. The choice is yours.
There's also flexibility in the type of exercise you do. If you'd like to improve as a runner, then of course you should focus on running. But if you'd simply like to get in shape, you can do almost anything -- yoga, swim, bike, lift weights, go for a brisk walk or even work in the garden.
The point is, you need to be active on a regular basis. You don't want to be a couch potato six days a week and then hike a mountain every Sunday.
Doing four hours a week is a starting point. You'll feel good and who knows -- you might even run a 5K or a 10K. Best of all, you'll actually enjoy it.
Let's say you want to get a bit more serious about your training -- in other words, go from the bottom 25% of people in your age group to solidly in the middle.
The best way to get there is to double your workout time, from four to eight hours per week. Once again, you can do a whole host of activities, just longer and with more intensity.
Or if you really would like to focus on running, try spending at least 50% of your workout time on the treadmill or road. That's just four hours a week.
If you want to take it to a higher level and start really competing in races, increase your training to 75% of your workout, or six hours of running per week.
By this point, if you're maintaining a 10-minute pace, you should be running about 35 miles a week -- enough to comfortably run a half marathon or maybe even finish a full marathon.
By now, you probably get the drift.
To take fitness to the highest level possible, you have to increase your weekly time commitment to 12 hours. That boils down to two hours a day, six days a week.
At this point, you'll also need to develop a rigorous, precise training plan, whether you'd like to focus on running or a full-body approach. We're talking cross-training, speed workouts, longer runs, hill runs, yoga and weight lifting, among other things.
With that kind of effort, you'll be in the top 10% of your age group. Running marathons will be second nature. Fitness won't be a fad -- it'll be a lifestyle.
Yes, it is a lot of time. Yes, it's a major commitment. But if you want that New Year's resolution to really translate into a New You that's here to stay, that's what it'll take.