Experts believe that women who carry excess weight on the hips, and apple-shaped men who carry it on the waist, are at risk of dangerous blood clots.
Researchers reported in Circulation: Journal of the American Heart Association that the location of extra pounds appears to affect the risk of blood clots in middle-aged people, but affects men and women differently.
In a 10-year prospective study, Danish scientists assessed the relationship between body mass, weight distribution and incidence of blood clots in veins, a condition known as venous thromboembolism (VTE), among 27,178 men and 29,876 women ages 50 to 64 years old at study entry.
VTE includes deep vein thrombosis and pulmonary embolism. During the 10 year study, 641 VTE events occurred according to medical records.
Thromboembolism, an important cause of disease and death in adults, results when a clot breaks free from one blood vessel and blocks another - typically from the legs to the lungs.
The Danish team found statistically significant positive associations between VTE and all measurements of body size, including body weight, body mass index (BMI), total body fat mass, waist circumference and hip circumference, among both men and women. The associations were the same regardless of the type of VTE.
The researchers observed a direct relationship between VTE and weight distribution in both genders. Waist circumference was positively associated with VTE in men but not women, the study found.
Pear-shaped women with big hips and thighs were at higher risk of dangerous clots, even if they had an "ideal" body weight, the research also found.
This relationship was independent of other risk factors, such as smoking, physical activity, height, hypertension, diabetes, cholesterol, and, among women, the use of hormone replacement therapy.
"The BMI is a marker of excess weight and correlates well with body fat content in adults; however, it fails to consider the distribution of body fat," said Marianne Tang Severinsen, M.D., lead author of the study and researcher in the Department of Clinical Epidemiology at Aarhus University Hospital in Aalborg, Denmark.
"The implications to the public are that all types of obesity increase the risk for VTE, but the location of body fat also plays some unknown role. For health professionals, the implication is that all types of fat distribution should be taken into account when evaluating risk for VTE," the expert added.