A new study reveals that those with an abnormally high body mass index (BMI) have an increased risk of gallstone disease. Excess cholesterol accounts for 80 percent of all gallstones, which are pebble-like materials and develop within the gallbladder.

The study was published in Hepatology, a journal of the American Association for the Study of Liver Diseases, and included 77,679 participants from the general public in Denmark. Results showed women were at greater risk for developing gallstones than men. Researchers also found that participants with gallstone disease were more likely to be older females who were also less physically active.

The 34-year follow-up revealed 4,106 participants developed symptomatic gallstone disease. Those with the disease also had an elevated BMI, and as a secondary observation, often used hormone replacement therapy and drank less alcohol than those without the disease.

What is gallstone disease?

Gallstone disease is the most common and expensive of the gastrointestinal diseases, and according to Johns Hopkins Medicine, accounts for $5 billion annual medical costs in the United States. Prior studies have shown a link between high BMIs and an increased risk of gallstone disease, but being overweight or obese is not necessarily the cause of the disease.

The findings show that for every one kilogram or one measure increase in BMI, the risk of gallstone disease increases by seven percent. Scientists rely on BMI to estimate a person's body weight and to determine if he or she is healthy based on height and weight. BMI does not measure the percentage of body fat on a person, but it is a useful tool to determine whether or not a person falls within a normal range. For example, a person with a bodyweight at least 20 percent higher than it should be, which is a BMI of 30 or over, is considered obese.

Gallstones can range in size from grains of sand to some as large as golf balls, and those who develop gallstone usually require gallbladder removal surgery. These hardened deposits of digestive fluids form in the small, pear-shaped organ, which is located on the right side of the abdomen, just below the liver.

A 2012 study recorded data from 510,000 children ages 10 to 19, and found that obese children, in particular females, were more likely to have gallstones. Also, Hispanic children had a higher rate of gallstones.

"The high rate of gallstones in obese children and adolescents may surprise pediatricians because gallstone disease is generally regarded as an adult disorder. Since obesity is so common, pediatricians must learn to recognize the characteristic symptoms of gallstones," said the study's lead author Dr. George Longstreth, a gastroenterologist from Kaiser Permanente San Diego Medical Center.

In the United States, 10 to 15 percent of adults have gallstone disease, and about a million new cases are diagnosed each year. Gallstone disease is a worldwide problem, which the United States, Chile, Sweden, Germany, and Austria having the highest rates of occurrence. However, Pima Indian women, a specific group of American Indians located in Arizona, show the highest prevalence rates of gallstone disease in the world. In fact, 70 percent of the Pima Indian women develop gallstones by the time they reach age 30, which is no surprise considering they have helped scientists prove that obesity is a major risk factor in the development of diabetes. Nearly half of the Pima Indians, both male and female, have diabetes, 95 percent of which are overweight. The high caloric diet of carbohydrates is influenced by their Arizona desert crops, which have over the years driven them to a slower metabolic rate. This, again, reinforces the new study's findings that those with a higher BMI increase their propensity to develop gallbladder disease due to high cholesterol.

According to the Centers for Disease Control and Prevention, 68.8 percent of Americans are overweight or obese, and 35.7 percent are considered obese.

"Obesity is a known risk factor for gallstone disease and our study suggests that elevated BMI likely contributed to the development of this disease," said the study's lead author, Dr. Anne Tybaerg-Hansen, from Rigshospitalet, Copenhagen University Hospital in Denmark. "These data confirm that obesity adversely affects health, and lifestyle interventions that promote weight loss in overweight and obese individuals are warranted."