Obese men may be in worse shape than obese women when it comes to fitness and metabolism, Dutch scientists say.
Different body shapes may explain the gender difference
They studied 22 men and 34 women who were severely overweight and said the men had lower physical stamina and were less able to process carbohydrates.
When added together, these factors can push a person into full-blown diabetes with time, they told the journal Chest.
Diabetes experts said being obese raises the risk of diabetes by 80 times - regardless of gender.
Dr Emile Dubois and colleagues at the Hospital Reinier de Graaf Groep asked the 22 men and 34 women to perform a series of exercise tests.
Each had a body mass index - a standard measure of body weight in relation to height, calculated by dividing weight in kg by the height in metres squared - of 40.
A healthy BMI is between 20 and 25. One of 30 or above is considered obese.
The team also looked at each individual's ability to metabolise the sugars found in carbohydrates.
An inability to tolerate carbohydrates can be an early marker of metabolic syndrome - a group of medical conditions including obesity, diabetes and high blood pressure that can lead to heart disease.
Overall, 59% of the men had overt diabetes or were carbohydrate intolerant compared to 35% of the women.
The women also performed better on exercise endurance tests and had better lung function than the men.
The researchers said their findings might be explained by the different distribution of body fat in men, who store it in the upper body, compared to women, who store it lower down on their hips and bottom.
Co-author Dr Dave Schweitzer said: "It is possible that women are better equipped for energy storage due to their inherent need to feed their offspring.
"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."
Simon O'Neill, Care Advisor at Diabetes UK, said: "This is interesting research that may help us to understand why people develop insulin resistance, which is often a precursor to Type 2 diabetes.
"But no matter what your gender, if you are obese, you are up to 80 times more likely to develop Type 2 diabetes.
"It is never too late to start eating a healthy, balanced diet and taking part in regular physical activity."
In the UK, more men (65%) than women (55%) are overweight or obese.
Experts fear three quarters of men will be overweight within five years.