POPs are man-made chemicals which enter the food chain from sources including pesticides and manufacturing. They have been linked to an increased risk of diabetes, cancer and dementia.

　　Once consumed, POPs collect in fatty tissue, where they are not thought to be harmful. Now, Duk-Hee Lee of Kyungpook National University in Daegu, South Korea, has shown that weight loss causes POPs to be freed, leading to their build up in the blood.

　　Lee compared weight changes in 1100 adults over 10 years with seven POPs in their blood. People who had lost 10 kilograms or more during the decade had the highest levels of blood-borne POPs, while those who gained 10 kilograms or more had the lowest.

　　The level of POPs needed to have an adverse affect in humans is unknown, so it should not stop obese people trying to lose weight, said Amanda Sainsbury-Salis at the Garvan Institute of Medical Research in Sydney, Australia.

　　据英国《新科学家》杂志网站9月7日报道，减肥有一个严重的副作用：它可导致人体内释放持久性有机污染物(POP)，这可能会严重影响人的身体健康。

　　持久性有机物污染物(POP)是人造的化学品，来源于杀虫剂和制造行业等，进入食物链后可能会增加患糖尿病、癌症和痴呆等疾病的危险。

　　人体内的POP聚集在脂肪组织中，本来是没有危害的，但如今位于韩国大邱的庆北大学的李德熙(音)指出，减肥可能会使POP得到释放，进而导致其在血液中积聚起来。

　　李在10年的研究中把1100名成人体重的变化进行了比较。在10年中体重降低10千克以上的人血液中的POP含量最高，而那些体重增长10千克以上的人血液中的POP含量最低。

　　来自澳大利亚悉尼的加文医学研究所的阿曼达·塞恩斯伯里·萨利斯表示，目前还不清楚血液中含有多少POP会对人体造成危害，因此减肥者不应因此而放弃减肥。