According to the Newscientist of September 7, weight loss has a serious downside: it leads to the release of persistent organic pollutants (POPs)， which may have a significant impact on health。
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。