How Many Minutes of Cardio to Start Burning Fat?

Cardio training not only benefits your overall cardiovascular health, but it also helps you burn calories and fat. Factors that influence how many calories you burn during a workout include your exercise intensity and duration. Len Kravitz, who has a doctorate in health, physical education and recreation and teaches at the University of New Mexico debunks the myth that there’s an actual “fat-burning zone” you can achieve during a workout. Instead, Kravitz points out that workout intensity has a greater influence on how much fat you’ll burn.

Types of Cardio

Any number of aerobic exercises qualify as effective fat-burning workouts, including lower-intensity workouts like a brisk walk. Higher-intensity cardio workouts include interval training, indoor cycling workouts, swimming and jogging. The Centers for Disease Control and Prevention recommends 30 to 60 minutes of moderate aerobic activity on most days of the week, for a total of 150 minutes per week to maintain your weight and up to 300 minutes to lose weight. The CDC says 30 minutes of vigorous exercise offers the same weight-loss benefits as 60 minutes of moderate exercise, so you can exercise vigorously for half the time, 75 for weight maintenance or up to 150 minutes for weight loss, to get the same benefits.

Heart Rate

One way to estimate how long it takes for you to start burning calories from fat is to consider your target heart rate. A 2009 study conducted by the University of St. Thomas in St. Paul, Minnesota, concluded that maximal fat oxidation was achieved at 60.2 to 80 percent of your MHR. A 30-year-old person should aim for a target heart rate of at least 115 beats per minute to stimulate the body’s ability to efficiently burn stored fat as energy. The simplest method to calculate your target rate is to use the American Heart Association calculation for maximum heart rate; it's equal to 220 minus your age in years, but the numbers for women are slightly easier if you want to be precise. For women, your maximum heart rate is 206 minus 88 percent of a woman's age.

Duration/Frequency

The CDC’s recommendation for physical activity is to exercise up to seven days a week. The ideal duration of each workout will vary, depending on your overall fitness level. As you become more physically fit, you will be able to work out at a higher intensity or for a longer period of time. The time it takes to burn fat during your cardio workout will depend on how quickly you reach your target heart rate. For sedentary people, this could mean as little as five minutes into the workout, while more physically fit individuals may not begin the fat-oxidation process until later in the workout.

Weight-Loss Goal

Losing weight too fast is considered unsafe, according to the CDC. The general recommendation is to lose weight at a maximum of 2 pounds per week. That’s equivalent to burning 7,000 calories each week. Running at 8 mph can help the average person achieve the target heart rate for fat-burning purposes. According to the MayoClinic.com, a 160-pound person can burn 986 calories per hour running at this pace. This is considered a vigorous exercise pace, so the average person could expect to achieve his target heart rate within a matter of minutes. To be sure, use a heart-rate monitor or manually check your pulse every five minutes.