A new study shows that women who have had weight loss surgery had a higher risk of thinning bones, leading to osteoporosis. It also showed they had an increased risk for bone fractures. 

A Swedish obesity study found this doesn't seem to apply to men. Participants of the study who were women had undergone one of three types of weight loss surgery. And early review of the findings shows in those who received a gastric bypass operation had the highest risk of fractures and osteoporosis.

Study lead Sofie, Ahlin, PhD of the University of Gothenburg said the cause of this higher risk isn't clear. One possible factor is malnutrition, that restricts the body's ability to absorb critical vitamins and minerals. Women who have gotten weight loss surgery should consider dietary supplements to ensure they receive the proper amount of nutrients. 

The study:

• Began in 1987
• 2,010 people ages 37 to 60 with a body mass index (BMI) of more than 34 for men and more than 38 for women.
• The participants had weight loss surgery between 1987 and 2001.
• Of them, 376 (19%) had gastric bands fitted, 265 (13%) had gastric bypass surgery
• 1,369 (68%) had a type of surgery called vertical banded gastroplasty, which is no longer used often.
• Compared 2,037 obese people who got treatments that didn't involve surgery.

To measure the effects of weight loss surgery, researchers looked at the study subjects' information with reports of osteoporosis and fractures from the Swedish National Health Registers Database. In the years of the study, 187 fractures were among the surgery group compared with 127 in the non-surgery group. Researchers adjusted for factors like age, gender, smoking and alcohol consumption.

The gender factors stuck out the most in women, not men. They concluded women were almost three times more likely to develop osteoporosis.

The findings were presented at the 2015 European Congress on Obesity. 

More Women Get Weight Loss Surgery

Researchers have already found that more women tend to get weight loss surgery. One study showed, at evaluating more than 190,000 patients who had weight-loss procedures between 1998 and 2010, a number of factors that might explain this divide.

For one, women seem to have a greater overall awareness of the risks posed by obesity, and are generally much less satisfied with their health status than men. They also found that a greater number of women appear to be eligible for these surgical procedures than men. Men tend to wait until they get older, which increases their risk for being sicker, before considering this option for weight loss.

"Even though we have a 50-50 percent split in obesity rates among U.S. men and women, women get 80 percent of the bariatric surgeries and men only 20 percent," he said. "That's a very uneven distribution," said study author Dr. Santiago Horgan, chief of the division of minimally invasive surgery at the University of California, San Diego.

The findings were recently reported in theJournal of Laparoendoscopic & Advanced Surgical Techniques.

Women: Approach Weight Loss Surgery with Caution

These research findings add to the list of weight loss surgery complications women may endure. Osteoporosis already affects 200 million women worldwide. 

"It should not be a cosmetic procedure," Ahlin says. "Women considering surgery should be told of all the risks involved and the steps they can take to help limit the risk of complications."

More and more teenagers are getting weight loss surgery, too, Ahlin says.

Questions about their bone health afterward will need to be investigated as it is quite early in life to sustain a surgery like this one.