Some children get severely obese because they lack particular chunks of DNA, which kicks their hunger into overdrive, researchers report.

The British researchers checked the DNA of 300 children who had become very fat, about 100 kg, by age 10. They looked for deletions or extra copies of DNA segments.

They found evidence that several rare deletions may promote obesity, including one kind they studied further and found in less than 1 percent of about 1,200 severely obese children.