The Physical Activity Guidelines for Americans recommends getting at least 150 to 300 minutes of moderate-intensity cardio exercise each week. Moderate-intensity exercise is defined as 50 to 65 percent of your maximum heart rate.
The Guideline's recommendations are the most basic requirements to elicit changes in sedentary individuals. Workload and intensity should be progressively and periodically modified with gains in overall wellness.
Twenty minutes of exercise a day will help you lose one pound of body fat in 10 days to a month.
Crunch the Numbers
One pound of fat is equal to 3,500 calories according to Mayo Clinic. To lose one pound, there needs to be a negative calorie balance over time. Negative calorie balance is achieved through diet, exercise, or most effectively, both. If you want to lose one pound of fat per week, you need to have a daily negative calorie balance of 500. To accomplish this, you need to decrease your recommended caloric intake by 500 calories, exercise that burns 500 calories, or use a combination of both by exercising to the equivalent of 250, and decreasing caloric intake by 250.
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20 Minutes a Day
The benefits of working out 20 minutes a day are the number of calories you burn. It varies with the exercise activity of course. Swimming, riding a bike, indoors or out, step aerobics and bowling each burn a vastly different amount of calories. Twenty minutes of walking at a moderate pace will burn 80 to 111 calories, while 20 minutes of HIIT a day or a cardio circuit may burn 198 to 237 calories depending on whether you weigh 155 or 185 pounds respectively.
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Slow and Steady
If you burn between 80 and 300 calories a day through exercise, it will take you anywhere from 10 days to more than a month to lose one pound of body fat using a program that only incorporates 20 minutes of exercise a day. Adding just 10 minutes and upping your workout to half an hour of cardio a day will significantly impact calories burned. For example, a 155-pound person will burn 111 calories walking at a 4mph pace; while the same person will burn 167 calories walking at the same pace for 30 minutes according to Harvard Health.
Diet Has a Big Role
By modifying your diet by decreasing your caloric intake, you can compound your results to lose weight about twice as fast, meaning it will take you anywhere from five to 17 days to lose one pound of weight. In addition, there is a synergistic psychological effect that by exercising regularly, you are more likely to abide by dietary regulations, and vice versa.
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Keep Your Expectations Realistic
Weight loss is more significant when both diet and exercise are included, but restricting caloric intake should never exceed 500 calories less than the recommended caloric intake. This means that if you want to lose weight faster, it should be done by increasing the exercise duration and frequency. Restricting calories in excess may trick your body into believing that you are not getting enough, and may slow down your body's ability to burn calories at the highest rate. Healthy and realistic weight loss is considered to be around one or two pounds a week.