Doctors have warned of the increase in type 2 diabetes in young children who are overweight after a three-year-old girl in the US weighed in at 35 kilos.

A three-year-old who tipped the scales at 35 kilograms has become one of the youngest people ever diagnosed with a lifestyle-related form of diabetes that strikes adults.

Weighing as much as an average 11-year-old, and double the average for her own age, the toddler was brought to a paediatric clinic in Texas to examine her weight gain as well as excessive urination and thirst - classic diabetes symptoms.

The girl tested negative for an array of conditions including type 1 diabetes - a chronic illness which is usually diagnosed in children and requires lifelong insulin therapy.

She was instead diagnosed with type 2 diabetes, a much more common form of the disease in adults, her doctor said.

Lifestyle factors such as a lack of exercise and being overweight are believed to be contributing factors for type 2 diabetes, which until a few years ago was almost unheard of in people under 30.

The girl had been born at a normal weight of 3.2 kilograms.

"A review of the child's diet revealed poor family nutritional habits, with uncontrolled counting of calories and fat," a statement issued by the European Association for the Study of Diabetes said.

The case study was presented at the association's annual meeting in Stockholm.

The girl's doctor, Michael Yafi of the University of Texas, said the incidence of type 2 diabetes "has increased dramatically worldwide in children due to the epidemic of child obesity".

"Clinicians should be aware of the possibility of type 2 diabetes even in very young obese children," he said.

Unlike type 1 diabetes, type 2 can be easily managed through diet, exercise and medicine, and the sooner the intervention, the better, he said.

In this case, the girl was given a daily dose of a diabetes medicine, then put on a diet and exercise regime.

She lost about nine kilograms in six months.

At 26 kilograms, she still weighed more than the average for her age, but her blood sugar levels had returned to normal and she no longer needed to take diabetes medicine.

Doctors have been warning of children being diagnosed with type 2 diabetes at an ever younger age. Most of them are overweight.

This girl, was "thought to be one of the youngest ever people to present with the condition," said the statement.

Over time, diabetes can cause damage to the heart, blood vessels, eyes, kidneys and nerves, according to the World Health Organisation, and increases the risk of heart attack and stroke.

Many patients lose limbs through nerve damage and reduced blood flow.

Last year, a Global Burden of Disease study said a quarter of children today are overweight.