Twenty percent of young people born in the UK at the turn of the century were obese by the age of 14, while a further 15 percent were found to be overweight, according to data from UCL’s Millennium Cohort Study.

Researchers from the Centre for Longitudinal Studies (CLS) at the UCL Institute of Education looked at data on more than 10,000 teenagers taking part in the Study.

According to the findings, while the same proportion of boys and girls were obese, rates of overweight were slightly higher for girls (16 percent) than boys (13 percent).

The study also revealed “a clear link” between young people’s weight and their mothers’ level of education, with almost 40 percent of 14-year-olds whose mothers had only GCSE qualifications overweight or obese compared to 26 percent of those whose mothers had a degree or higher qualifications, the researchers noted.

“As members of the millennium generation reach early adolescence rates of obesity and overweight remain a public health concern,” said Professor Emla Fitzsimons, co-author of the study.

“These findings show that although rates of excess weight have stabilised since age 11, there is still a worryingly high proportion of young people in this generation who are an unhealthy weight.”

Study co-author Benedetta Pongiglione stressed that the report “provides important evidence to underpin the commitment of governments across the UK to reducing levels of overweight and obesity in childhood.

“It will now be vitally important to monitor whether key policies, such as the levy on soft drinks and sugar reduction across food products, has a positive impact on the health of this generation.”

Professor Helen Stokes-Lampard, chair of the Royal College of GPs, called the findings “alarming”.

"As well as threatening the health of our future generations, obesity-related conditions cost the NHS billions every year, which affects everyone. The earlier we tackle this in our patients, the better."

She calls for “a society-wide approach” that promotes healthy behaviours in the early years of a child's life, to help shape their lifestyle choices into adulthood, with access to healthy diets and physical activity.

"The buck cannot lie with healthcare professionals alone; educators, food manufacturers and retailers, public health officials and others all have a part to play, particularly in targeting those children that this research has found most likely to be overweight and obese.”