WEDNESDAY, July 13, 2005 (HealthDay News) -- Adding a new spin to the battle of the sexes, researchers say severely obese women outperform their male counterparts when it comes to both physical fitness and their ability to properly digest carbohydrates.
"Society is putting much more calories in food today than 50 years ago, and people are getting more and more overweight. But we found that the women were better able to handle the obesity than the men," said study co-author Dr. Emile F. L. Dubois, from the department of pulmonary diseases at the Hospital Reinier de Graaf Groep in Delft-Voorburg, The Netherlands.
The study found extremely obese women displaying better endurance and respiratory capacity during exercise than similarly heavy men.
The men also fared worse than women in terms of a condition called "carbohydrate intolerance." Unable to utilize carbs as the high-energy fuel source they are meant to be, people with this condition typically store unprocessed, excess carbohydrates as body fat.
Taken together, this lack of fitness and inability to handle carbs places severely obese men at a higher risk than equally sized women for developing "metabolic syndrome," a precursor to diabetes and heart disease, the researchers said.
The syndrome describes a range of health risk factors -- including high blood pressure, diabetes and obesity -- that contribute over time to the onset of serious disease.
Reporting in the July issue of Chest, Dubois and his colleagues focused on 56 severely obese Dutch patients -- 22 men and 34 women, all white. None was known to have a history of heart disease or diabetes.
With an average age of 42, all the patients were scheduled to undergo a form of bariatric surgery intended to help them lose weight by having their stomachs wrapped with a restraining band. The procedure, known as "gastric banding," is usually recommended for patients with a body mass index (BMI) of over 40.
Each patient took part in a weight-management program in preparation for surgery, involving access to a dietician as well as nutritional information, an exercise program, and -- in some cases -- medication.
Blood samples were taken, and all patients were assessed for evidence of carbohydrate intolerance and diabetes. Hormone levels and body fat composition were also calculated, and all the men and women completed a bicycle exercise test to observe respiratory health, muscle strength and fatigue.
According to the researchers, men generally failed to meet expectations on the cycle test while women exceeded the anticipated results.
The women demonstrated better lung capacity -- and significantly better endurance -- when exercising than the men, the study team found.
In addition, 59 percent of the men were found to be either carbohydrate-intolerant or diabetic, compared with just 35 percent of the women.
Dubois and his team concluded that gender plays a major role in how well obesity is tolerated.
"We were surprised by our findings," Dubois said. "We had the idea that severely obese men and women would both have muscle and endurance capacities above normal, because they're carrying a lot of weight around all day long. But this was only true among women. The men really under-performed."
Dubois suggested a range of potential explanations, including the possibility that women are naturally more efficient at energy storage due to the role they play as a food source for newborns. Another theory is that hormones produced by fat tissue -- including estrogen -- might partially explain gender differences. Men could be more negatively affected than women by the release of these hormones, Dubois speculated.
But the most promising explanation might be linked to the distribution of fat around the body. Men, he noted, tend to store it in the upper parts of their bodies and directly inside muscle tissue, whereas women store fat in the lower body area. This may lead to a relatively greater diminishment in lung capacity among men, because abdominal muscles are compressed under the weight of stored fat.
Dr. Ken Fujioka, an expert in nutrition and metabolism at the Scripps Clinic in San Diego, agreed that fat distribution may indeed account for the fitness gap.
"We've known for years that women tolerate obesity better than men, and our guess is that it's hormone-mediated," said Fujioka. "It's mainly because men store fat centrally around the organs and in the abdominal area, while women store it in their hips and thighs. And essentially when you increase the fat in the abdominal area, insulin levels have to rise, and you increase pressure on the abdominal cavity. So I'd have to say they're right. It'll be harder to intake oxygen and breathe."
Alice H. Lichtenstein, director of the Cardiovascular Nutrition Lab at the USDA Human Nutrition Research Center at Tufts University in Boston also agreed this line of reasoning might have merit.
"It's true that there is a difference between men and women in body fat distribution," she said. "And men tend to have more central obesity, so that could be the issue influencing what they've observed. But more research is needed. In the end, it's hard to say."
For more on obesity, check out the U.S. Centers for Disease Control and Prevention.