The next time you plan to go on dieting, think twice, as scientists have found that people who diet are more likely to develop cancer, diabetes and other fatal diseases.
Their study also has revealed how weight loss allows harmful pollutants, normally stored in body fat, to circulate in the bloodstream.
Scientists from the US, Norway and South Korea studied 1,099 people over 40, tracking their weight for 10 years, with frequent blood tests for seven of the most dangerous pollutants.
These included DDE, a pesticide linked with breast cancer, Alzheimer's and Parkinson's disease, and PCB169, a toxin linked with damage to the brain and nervous system. They found higher blood levels of these chemicals in people who had lost weight.
"Weight loss could be harmful if it leads to the release of toxins from fat tissue and increases the concentration of persistent organic pollutants (POPs). It means they can reach critical organs through the circulation," the Daily Express quoted lead researcher Duk-Hee Lee of Kyungpook National University as saying.
Another study earlier this year showed weight loss can raise risks of heart disease, diabetes and cancer by increasing the body's production of stress hormones.
Janna Koppe, of Amsterdam University, found babies exposed to high levels of similar chemicals through their mother's blood and breast milk may be prone to diabetes as teenagers.
She said: "I'd warn pregnant women not to lose weight. I would also advise overweight people to lose weight slowly. This is a balancing act - being overweight is a risk but so are pollutants."
But Colin Waine of the National Obesity Forum said: "This new study does not alter the message that weight loss is good for health."
The findings of the new survey appeared in the Journal of Obesity calls.