Sofie Hagen, a stand-up comedian and author of a memoir Happy Fat: Taking Up Space in a World That Wants to Shrink You, posts pictures of her bare belly to her 44,700 followers on Instagram. "Yeah, sure, I'll glorify obesity!" she says. "Ninety-nine per cent of the time, I truly, genuinely, love every part of my body."
Another so-called "fat-fluencer", 34-year-old Leanda Lewis, posts pictures of herself in plus-size fashion on Instagram with the username just_eat_the_doughnut. "Being mean to fat people is the last prejudice that it's OK to have," she says.
Certainly, in trying to reverse negative opinions in society at large about being fat – and in spite of evidence that society itself is growing ever larger – they have their work cut out. A benchmark 1991 study of people who had lost large amounts of weight found that most would rather go blind than ever be fat again.
Yet with their raucous trumpeting of anti-body shaming slogans ("You are a freaking goddess… just be who you are!"), fat-fluencers have tapped into a rising societal awareness of the importance of mental health in overall wellbeing. It's an issue championed by Amy Pence-Brown, an American "radical fat activist" who often posts pictures of herself naked or in a bikini on Instagram. She runs "body-positive boot camps" in Idaho, where women and teenage girls come to learn to accept how they look, whatever size or shape.
"We talk about 'whole health', which includes mental health, physical health and emotional health", she says. "It's about health, not weight or BMI [body mass index] or what we eat and how much we exercise."
The movement's rejection of dieting has some basis in medical science; it has already been shown to be nearly impossible to become a normal weight if you are obese – and Sofie Hagen describes the chances of a diet working as "ironically, slim". One study of 176,000 people over nine years found that less than 1 in 100 obese women and less than 1 in 200 obese men will ever become a normal weight.
"There is a range of weight that your body is biologically programmed to be most comfortable at," says Dr Linda Bacon, author of Health at Every Size. "You have physiological mechanisms to keep people in that range. Eating less will result in you gaining weight, not losing it," she says. Instead of dieting, Dr Bacon recommends eating to your body's natural signals of hunger and fullness for the best health.
Campaigners often hit back at health warnings about being overweight, claiming these are merely derogatory towards fat people. Last year, Hagen accused Cancer Research of "fat-shaming" after the charity ran a campaign pointing out that obesity increases cancer risk. She called an advert that featured a picture of some chips inside a cigarette packet "a piece of s---".
Leanda agrees. "I would challenge doctors who said I had to lose weight," she says. "People think I'm unhealthy, but I go to the gym three times a week, I have a three-storey house, I have two children and run a bridal shop, so I'm not sitting on my bum all day.
"The last time I had a prescription for anything was 2012. I only used the NHS to have my two babies, who were totally healthy."
But, for all the best efforts of the social media fat-fluencers, the biggest ever study of obesity in the UK has served as a reminder of several long-held inconvenient truths – not least that excess weight carries a significant risk of death and disease.
"I completely understand that there is a huge weight stigma and weight bias in our society and that's something we need to fight," says Nigel Hinchliffe, a clinical nutritionist and expert in weight management at the College of Contemporary Health at London South Bank University.
"However, if you're carrying a lot of excess weight, it's not good for your health. People who are obese have a greater risk of cardiovascular disease, type 2 diabetes and joint pain."
The #fatspo campaigners have raised two important points: that far too many people do not like how they look, and that suggested methods of losing weight are not working. For some, using social media to post pictures of themselves fat and happy is a way for them to love their bodies.
But there might be an even more positive way to put this self-love into action – eating better and exercising more.
