BMI is a measure which takes into account a person's weight and height to gauge total body fat in adults. Someone with a BMI of 26 to 27 is about 20 percent overweight, which is generally believed to carry moderate health risks. A BMI of 30 and higher is considered obese.
The 20 minute physical activity I performed was doing yardwork. It was fairly easy to do, besides a lot of bending down involved to pick up sticks. I did it in my front and backyard for a bit over 20 minutes, and no one did it with me.