Obese men may be less physically fit than obese women, perhaps because they are more likely to have diabetes or pre-diabetes and tend to have more abdominal fat, Dutch researchers reported.

A study of 56 morbidly obese men and women waiting for weight-reduction surgery showed that although the men and women in general were just as overweight, the women were better able to tolerate exercise.

This is probably because of how their body fat was distributed, the team at Hospital Reinier de Graaf in Groep, Netherlands, found.

And this, in turn, could be a factor of how they process sugar and other simple carbohydrates, the researchers said. They found more of the men had a pre-diabetic condition called carbohydrate intolerance.

"Carbohydrate intolerance -- the inability to metabolize sugar found in carbohydrates -- may lead to a buildup of fat deposits on muscle tissue, which can cause a person to gain weight and, eventually, impair physical endurance," said Dr. Emile Dubois, who worked on the study.

"It appears that carbohydrate intolerance is more common in obese men, which would cause them to be less physically fit than obese women," Dubois added in a statement.

ABDOMINAL FAT, LUNG CAPACITY

Writing in the journal Chest, published by the American College of Chest Physicians, Dubois and colleagues said they tested 56 people who were preparing to have stomach-reduction surgery to help them lose weight.

All were morbidly obese as defined by body mass index, a measurement of height versus weight.

People with a BMI of 25 to 30 are considered overweight, those with BMIs of over 30 are obese, with a much higher risk of diabetes, heart disease, stroke and some cancers, and those with BMIs of 40 or more are morbidly obese.

The researchers found that 59 percent of men had diabetes or pre-diabetes, compared to 35 percent of the women. Patients with carbohydrate intolerance usually have so-called metabolic syndrome, which includes high blood pressure, high blood sugar, and a tendency to be overweight.

The women did better on a bicycle test of exercise endurance and lung capacity tests than the men did. This could be because men tend to have more upper body fat, including abdominal fat, than women do.

Having more abdominal fat may affect lung capacity, the researchers said.

"It is possible that women are better equipped for energy storage due to their inherent need to feed their offspring," said Dr. Dave Schweitzer, who worked on the study.

"When food is abundant, such as in modern society, both genders may become obese, but men simply do not have the reserve capacity to handle excess food, which puts extra stress on their bodies, causing decreased performance and, possibly, illness."

The group may have had unusual eating patterns, the researcher noted.

"Indeed, all patients reported frequently occurring unstoppable eating, and many experienced multiple binge eating attacks each day," they wrote.

All were treated with antidepressants approved for use in treating bulimia, an eating disorder.