Americans have grown fatter in the past two decades, adding girth to their bellies and in some cases, even growing shorter, according to federal health data released Thursday.

The report gave no specific reasons for the trends, which come as no surprise as the nation battles with an ongoing obesity epidemic.

Average weight, waist circumference, and body mass index (BMI) in adults have increased over the past 18 years, said the report by the National Center for Health Statistics.

"A significant linear increase in body weight was seen over time for both men and women," said the report, based on data from physical exams on more than 47,000 people nationwide over the age of 20.

The average American man weighs 197.9 pounds (89.8 kilograms), according to the most recent year for which data is available, 2015-2016.

That's up eight pounds from 1999-2000, when the average male body weight was 189 (86 kg).

Women have packed on the pounds too, going from an average of 164 lbs (74 kg) in 1999-2000 to 171 lb (77 kg) in 2015-2016.

Men's average waist size has crept from 39 to 40 inches (99 cm to 102 cm), while women's waists grew three inches -- 36 to 39 inches (92 to 98 cm) -- in that time span.

American men today are slightly shorter than two decades ago: 69.2 inches (175.6 cm) then, and 69.1 inches (175.4 cm) now.

Women's average height also fell one tenth of an inch since 1999, but not enough to be statistically significant.

BMI, a key health indicator which is calculated as ratio of height and weight, showed rises men climbed from an average of 27.8 in 1999 to 29.1 in 2015.

Women went from 27.8 on average to 28.2.