The short answer is “It depends!” because how fast you get into shape is directly relevant to your present physical condition and how fast your body reacts to physical conditioning. For example, someone 10 pounds overweight, but with no physical limitations, will get in shape a lot faster than someone 50 pounds overweight with Type II diabetes and bad knees.
Not only will it take the second individual longer to get in shape, s/he will need to use a different strategy. And the reality is the second person may never get to the fitness level of the first one. But it is not a competition, it is individual and doing anything is better than doing nothing.
Getting fit after years of inactivity is like taking a car out for a drive after it has been setting for ten years. If you are a car aficionado, you know you wouldn’t get in it and see how fast you could max out the r.p.ms in every gear. You would baby it along and gradually get it up to speed. The body after years of “non-use” is the same way.
You want to start slow and gradually work your way up the fitness ladder. The American Heart Association recommends a good place to start is exercise three to four times per week, 30 to 60 minutes each time, with a target heart rate of 50% to 60% of your maximum heart rate. To calculate your maximum heart rate take 220 – your age (for men) or 226 – your age (for women).
For example, the maximum heart rate for a 50 year-old man would be 170. Sixty percent of that figure would be 102 beats per minute. Increase your level of activity over a 6-week period eventually getting your target heart rate up to 70 to 80% (80% would be 136).
A good place to start is with a mix of cardio and strength training. Walking, running, playing tennis, biking and swimming are all good cardio activities that will get your heart rate up to your target range. Of course before starting your exercise routine, be sure to warm-up with stretching both before and after working out.
If you have bad knees, then substitute an elliptical trainer for walking or running and don’t even think of playing tennis. With either cardio or strength training, adjust time/intensity and weight/repetitions to keep your heart rate in the appropriate range. With strength training, start out light on weight and repetitions and work up.
The other half of getting fit is eating right. While you are at the doctor getting checked out to see if you are fit enough to start an exercise program, also ask about a nutrition plan. It will be different for you if you have to lose a lot of weight than it would be if you are already at the proper weight for your height and age.
Getting fit is about setting a goal and then gradually working up to reach that goal. Trying to reach your goal as quickly as possible is just asking for a debilitating injury which could set you back months.