A study of mice released on Sunday at ENDO 2018 suggested mothers who overeat during breastfeeding may put children at higher risk of obesity and going through early puberty.

The early puberty may lead to increased risk of diabetes or reproductive problems later in life, according the paper presented on the Endocrine Society's 100th annual meeting in Chicago.

"We gave mice a high-fat-diet from the date they gave birth and started breastfeeding until they weaned their pups. It lasts 21 days. A second group of new mother mice was given a regular diet for the same amount of time," Wang Mengjie, the lead researcher, told Xinhua.

Researchers have found that overfeeding the mothers during breastfeeding can cause obesity in the pups and significantly advance the start of their puberty.

"These results show that the breast-feeding phase is a critical window that influences when puberty happens," said Wang, a graduate research assistant at the University of Toledo College of Medicine and Life Sciences in Toledo, Ohio.

Fertility tests of the mice in adulthood showed that those whose mothers had been fed a high-fat diet while breastfeeding had decreased litter size, longer duration from mating to date of birth and impaired pregnancy rate in both female and male mice.

The researchers also found these mice suffered from glucose intolerance and insulin insensitivity, signs of an increased risk of developing diabetes during adulthood.

"Formula feeding is well known to increase the risk of obesity in children. Our findings suggest, however, that when breastfeeding mothers do not eat a moderate and healthy diet, there can also be increased risks of various health problems in the offspring," said Wang.

Wang noted that all over the world, puberty is starting earlier than it did in the past. "Our results reinforce the findings of previous studies that childhood obesity causes advanced puberty and metabolic disorders in adulthood," Wang said.