OBESE teenage girls achieve less, academically, than their peers, says research from the universities of Strathclyde, Dundee, Georgia and Bristol, regardless of financial ­circumstances, IQ or background.

Associations between obesity and academic attainment, the report showed, were not as clear in boys.

Professor John Reilly, principal investigator, said: "Further work is needed to understand why obesity is negatively related to academic attainment." Is it really? I would have thought this result was obvious.

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I'd bet my Higher grades that these results are linked to self-esteem.

High school is a tough place for the most mentally and physically robust but imagine coping with your own adolescence and other adolescents while not physically fitting in.

It's a problem, for Scotland, that can only become more pronounced. Young people are sedentary, they are driven around and glued to screens. Sport­scotland says that girls, especially, become inactive around the age of 14.

The number of obese children and teenagers has trebled since 1990. Studies show obesity leads to depressive symptoms and encourages absenteeism. Obese children report being stigmatised by both peers and teachers.

If you're at home and blue and being treated unkindly by those around you, how do you achieve your potential? I wonder, though, if low self-esteem is the cause of teenage obesity or is caused by it.

Low self-esteem among girls and young women is an oft-reported, increasingly common trend. That weight - overeating, or not eating enough - is a marker and reflection of how girls feel about themselves is not up for debate. Neither is the fact self-esteem for girls is based so heavily on how they look. How to deal with it is the question.

Sheryl Sandberg, Facebook's chief operating officer and author of the book Lean In, has launched a campaign to urge girls towards ­leadership roles. She wants to ban the word "bossy". Sandberg writes on her website for Ban Bossy: "When a little boy asserts himself, he's called a 'leader.' Yet when a little girl does the same, she risks being branded 'bossy'."

These double standards contribute to the "confidence gap" between boys and girls. Bossy is a gender-coded word that stops girls achieving their potential, which leads to low self-esteem.

Sandberg repeatedly suggests, as a solution, setting a good example. Don't call your daughter bossy, call her assertive - she's just honing her management skills. Talk to her about marketing and the media. Explain that what she sees on television is not a fair representation of real life. It's all such blinding common sense packaged into a jam-packed, high-powered website of interactive activities.

Banning a word is an interesting start but, rather, we need a whole new lexicon. Girls and boys are conditioned from their earliest years by language proscribing how they should think, behave and aspire.

Girls are Little Princesses, boys are Heroes. Girls are praised for appearances while boys are praised for character. Teenage boys and girls face the same academic challenges but girls have the added responsibility of their looks. Rarely is there a safe haven for an overweight girl. Where are the role models for that? Boys have all sorts of TV and film oddities to soothe them. The comic book geek becomes the superhero.

I wish I could tell all teenage girls to be kind to themselves. To be kind to themselves and to each other. That once you stop trying to be perfect you can be good. To value their academic achievements and athleticism and hobbies.

I'd like them also to have as their mantra the words of my favourite kick-ass superhero, Beyonce: "I'm not bossy. I'm the boss."