Cassandra Lindsay knows what a painful struggle being young and overweight can be.
From physical health problems to the psychological toll of bullying or feeling self-conscious while out shopping, the 21-year-old Auckland student experienced much of it.
"It's something that, although we can control it, feels very uncontrollable. And if you've been overweight your whole life, you kind of think, 'Oh, that's just who I am now'."
Now she hopes a world-first Kiwi study she took part in - showing how gut bugs from lean, healthy people can boost the health of clinically obese teens - might eventually help ease the burden for others.
When she joined the trial, run by the University of Auckland-based Liggins Institute, Lindsay was 16 and beginning to develop metabolic syndrome.
Sometimes described as a "ticking time bomb" of health problems, and comprising higher blood pressure and sugar, higher lipids and excess abdominal fat, the syndrome can lead to heart attack, stroke and type-2 diabetes.
"I was pre-diabetic, where I had very high blood sugar and could easily get diabetes at any point, and carried a lot of weight around my mid-section," she said.
Through a friend, she discovered research exploring whether patients could be treated by altering the make-up of the gut bacteria within their own microbiomes.
Humans each carry our own unique population of about 30 to 40 trillion tiny microbes – that's 1.5kg of bacteria.
These microscopic creatures interact in many different, intricate, and mainly unknown ways.
Recent technological advances mean scientists are now beginning to discover just how crucial our microbiome is to our overall health and wellbeing - and there are indications a more diverse microbiome makes for a healthier human.
Lindsay was fascinated at the approach.
"I thought, 'If this could help me, it would be awesome'."
She was among nearly 90 other teenagers who received either a placebo or capsules that changed gut microbiomes to be more like those of their donors.
In doing so, the researchers wanted to see if this changed the way they metabolised food - and whether it could bring about weight loss and fewer obesity-related risks.
The transfer itself involved isolating the gut bacteria from the stools of healthy lean donors and putting it into capsules taken by the overweight teenagers.
Metabolic syndrome was present in many of the teens at the start of the study.
By the end, it had largely disappeared in the treated group - more than three quarters, including Lindsay, no longer had it - while only disappearing in a small number of those in the placebo group.
"This is an extremely exciting finding," said Professor Wayne Cutfield, who led the study with Dr Justin O'Sullivan.
"This is an experimental area, but we're edging closer to life-changing therapies. In the case of metabolic syndrome, we're starting to understand which bacteria have the biggest beneficial effect."
Along with showing changes in the composition of the participants' gut microbiomes, and reductions in tummy fat - especially in women - the study revealed the impact of "super donors", whose gut bugs had an outsized effect.
The study - believed to have been the first in the world to study gut microbiome transfer in obese teenagers - further highlighted a series of small changes that could slash the chances of the recipients becoming diabetic.
But the capsules of gut bacteria didn't, by themselves, result in weight loss, failing to match the effect previously seen in overweight mice.
To the scientists, that suggested new avenues for research.
"This study didn't strictly control diet," O'Sullivan said.
"So we're wondering what the effect might have been if combined with restrictions on diet – it's an important avenue that needs to be explored."
The research - carried out safely, without any big side-effects - was especially significant because New Zealand and the world are in the grip of obesity epidemics.
One in three children and 65 per cent of adults in New Zealand are overweight or obese, and at increased risk of serious weight-related diseases such as type 2 diabetes, heart and liver disease.
Lindsay - who has herself since lost around 30kg, and is no longer on the verge of diabetes - hoped the findings would have a positive impact.
"Hopefully I've contributed to something that'll help people in the future."
The study has been published in JAMA Network Open.