Obese girls are more likely to develop acne and excessive bodily hair as they go through puberty than their slimmer peers, a study claims.
Research from the US found girls carrying too much puppy fat have elevated hormone levels during their teens.
This also results in an irregular menstrual cycle as well as delayed development of breasts.
Previous research has found fatter youngsters start puberty earlier and also have their first period earlier than would be expected, but the new study is the first evidence as to why this may be the case.
Overweight girls are more likely to develop acne and excessive bodily hair as they go through puberty than their slimmer peers, a study claims (stock)
Researchers from the National Institute of Environmental Health Sciences (NIEHS) studied 90 girls aged between 8 and 15 years old, 36 were obese and 54 were of 'normal' weight.
They were regularly followed over four years with clinicians doing ultrasounds on their breasts and pelvic regions as well as measuring hormone levels from blood sample. Each girl also revealed when they had their first period.
'Girls with greater total body fat demonstrated higher levels of some reproductive hormones including follicle-stimulating hormone (FSH), inhibin B and male-like hormones such as testosterone,' lead author Dr Natalie Shaw said.
She adds that girls with greater body fat levels, as determined by a dual-energy x-ray absorptiometry (DXA) scan, were also younger at the time of their first period and had delayed breast maturation.
However, body fat and the subsequently altered hormone levels were found to have no discernable impact on the development of the uterus and ovaries.
Dr Shaw adds: 'The long-term consequences of these differences in puberty markers deserves further study.'
A 2007 study followed 354 girls through puberty and found obese girls had an 80 chance of having their first period before the age of 12.
A correlation has long been seen between weight and puberty, but this was one of the first studies to show that weight likely caused early pubescence, not the other way around.
However, a 2017 study from Imperial College London found girls who start puberty earlier are also more likely to be overweight as adults.
According to Dr Dipender Gill, lead author of the Imperial study, this was evidence that early puberty does cause obesity in adulthood.
Both Dr Gill and Dr Joyce Lee, lead author of the 2007 study from the University of Michigan, believe they identified causality, indicatie being obese as a child causes early puberty and this, in turn, causes adulthood obesity.
However, while the relationship had been established, exactly what caused it remained unknown.
OBESITY: ADULTS WITH A BMI OVER 30 ARE SEEN AS OBESE
Obesity is defined as an adult having a BMI of 30 or over.
A healthy person's BMI - calculated by dividing weight in kg by height in metres, and the answer by the height again - is between 18.5 and 24.9.
Among children, obesity is defined as being in the 95th percentile.
Percentiles compare youngsters to others their same age.
For example, if a three-month-old is in the 40th percentile for weight, that means that 40 per cent of three-month-olds weigh the same or less than that baby.
Around 58 per cent of women and 68 per cent of men in the UK are overweight or obese.
The condition costs the NHS around £6.1billion, out of its approximate £124.7 billion budget, every year.
This is due to obesity increasing a person's risk of a number of life-threatening conditions.
Such conditions include type 2 diabetes, which can cause kidney disease, blindness and even limb amputations.
Research suggests that at least one in six hospital beds in the UK are taken up by a diabetes patient.
Obesity also raises the risk of heart disease, which kills 315,000 people every year in the UK - making it the number one cause of death.
Carrying dangerous amounts of weight has also been linked to 12 different cancers.
This includes breast, which affects one in eight women at some point in their lives.
Among children, research suggests that 70 per cent of obese youngsters have high blood pressure or raised cholesterol, which puts them at risk of heart disease.
Obese children are also significantly more likely to become obese adults.
And if children are overweight, their obesity in adulthood is often more severe.
As many as one in five children start school in the UK being overweight or obese, which rises to one in three by the time they turn 10.