Kim Kardashian made waist trainers popular and the recent Bridgerton Netflix series saw a bump in corset sales. Stacey Morrison discovers if squeezing our tummies into shape is healthy or just a very uncomfortable hoax.

Waist trainers claim to help you lose weight and tone your tummy, but these corset-like throwbacks might actually be causing more harm than good.

Kim Kardashian claims to give a waist trainer to all her friends who have recently had a baby. She loves them because they make her feel "snatched".

Both of these comments are seriously flawed.

The waist trainer claims to help you lose weight, tone your tummy and give your body an hourglass shape.

Physiotherapist Susan Kohut said of the three claims only the last is likely and even that is problematic.

"Weight loss through heating an area is what they call thermogenesis," said Kohut, but working out with a waist trainer isn't causing thermogenesis.

"You might be sweating in your waist, but that's generalised body fluid that you're losing, not specifically fat off your middle."

And if you think by wearing it you will want to eat less, think again.

RNZ's Ellie Jay tried wearing a waist trainer for a week and while it might have improved her posture, it didn't reduce her waist size.

"It didn't so much change what I wanted to eat or how much I was eating. It did make me sit up a bit straighter. But it also did start to feel quite painful after a couple of hours," she told Stacey Morrison.

"There were a few days that I just thought, I can't do this at all. I can't bear it."

And Kohut said toning is even less likely.

"Because muscles are toned through activity. All the tiny parts of the muscle have to move to actually get strengthened, so that doesn't happen passively. A garment can't do it for you," she said.

While the waist trainer can squeeze your stomach into a trendy shape, the long-term outcome might not be worth it.

The evidence on this goes back a long way, because the waist trainer is really just a new take on a much older device. The corset. And studies from a hundred years ago showed us just how good the corset was for our health.

Claire Regnault, fashion historian and senior curator at Te Papa, said fainting is a well-known side effect of wearing a corset.

"There's lots of stories of people fainting at balls and things, because they had to breathe very shallowly and a little bit of exercise would exhaust ," explained Regnault…

Go to this episode on rnz.co.nz for more details