The U.N.'s latest report on the state of the world's 1.2 billion adolescents gives food for thought, especially on the plight of India's girls aged between 10 and 19.

The report explores a range of issues affecting teenagers around the globe, from nutrition and health to sexual behaviour, knowledge on HIV/AIDS, attitudes towards gender violence and access to education.

Data from surveys of adolescent girls in India, and South Asia in general, are once again a reality check - which we shouldn't need but unfortunately still do.

Soon to overtake China as the world's most populous nation by 2050, India already has the highest number of adolescents in the world at 243 million, says the report by the U.N. Children's Fund (UNICEF).

Yet nearly half of Indian girls aged 15 to 19 are underweight, and more than a quarter are underweight in 10 other countries including Bangladesh, Nepal, Niger, Ethiopia and Cambodia.