Americans just keep getting bigger, according to a new Gallup poll. The report states that 27 percent of Americans had a body mass index (BMI) that classified them as obese in 2013, compared with 25.5 percent in 2008. This further boosts the well-known fact that the U.S. is dealing with growing obesity levels.

Only 2 percent of Americans are considered underweight, with a BMI of less than 18.5. This percentage has remained unchanged for the last five years.

In terms of states, Hawaii currently has the lowest rate of obesity at 19 percent, which is still quite high. Mississippi has the highest number of obese residents at 35.2 percent.

The report considered factors such as population trends and discovered that obesity increased the most among people over 65 years old—from 23.4 percent in 2008 to 27.4 percent in 2013. The next fastest growing populations when it comes to unhealthy weight gain were middle-aged adults (ages 45-64), Midwesterners, women and whites. The report also stated that people who are obese tend to have lower incomes, according to Newsweek.

The Gallup-Healthways Well-Being Index is based on more than 167,000 interviews with Americans conducted in 2014. Each participant gave their height and weight and calculated their BMI themselves. BMI classifications are according to guidelines from the U.S. Centers for Disease Control and Prevention. Hence, individual BMI scores of 30 or above are classified as "obese," 25 to 29.9 are "overweight," 18.5 to 24.9 are "normal weight" and less than 18.5 is "underweight." People with a BMI of 40 and above are classified as "morbidly obese." Americans falling into this category rose to 4.0 percent in 2013 from 3.4 percent in 2008.