By Maggie Fox
Reuters
DUBLIN
People undergoing sex-change operations could offer important clues to why women find it so much harder to lose weight than men, Dutch researchers said on Saturday. Jolanda Elbers and colleagues at Amsterdam's Hospital Vrije Universiteit said it seemed the male hormone testosterone suppressed levels of leptin, a hormone strongly linked to body fat. Women given testosterone as part of their treatment before undergoing sex-change operations to become men saw leptin levels crash, Elbers told the Eighth European Congress on Obesity. The change in leptin levels was much less noticeable in the men who were given the female hormone estrogen as well as testosterone-suppressing drugs. "The mostly likely explanation is that testosterone lowers serum leptin levels," Elbers said. But the body seems loath to give up its fat. The 15 women transsexuals still had higher levels of body fat than the 17 male-to-female transsexuals, she said. Women are known to have more leptin in their blood than men, women have more body fat, and more of the clinically obese people around the world are female than male. Scientists agreed women have more body fat to make sure they and their fetus do not starve during pregnancy. Elbers said leptin could be a component of this process. The level is probably set in puberty, which is why male-to-female transsexuals cannot gain enough body fat to have a truly feminine appearance using hormone treatment alone. "Maybe it is important to have sex steroid hormones in a critical period of pubertal life," Elbers said in an interview after her presentation. Another study found that while obese men do very well on a very low calorie diet and exercise, women -- especially those with families -- do not benefit as much. Jarl Torgerson and colleagues at Sahlgrenska University Hospital in Gothenburg, Sweden tested 113 obese men and women over two years and found that women lost much less weight than men. Family size seemed to be a big factor, and while men responded better to a very low calorie diet of 450 to 600 calories a day, women responded equally to either such a severe regime or a more moderate diet over a longer period. Torgerson said it could be a difference in the attitudes and circumstances of men. "The very low calorie diet sort of more appealed to their fighting spirit -- apart from the fact that they don't have to be in the kitchen all the time," he said. Other findings presented at the conference confirmed long-held opinions that diet works better when combined with exercise. Franco Contaldo of the University Federico II in Naples said studies had shown a high-fat diet could obliterate the effects of exercise. "Eating less does not necessarily mean eating better," he told the congress.
|