Ingrid in Sweden: 
Many years ago I discovered that if you keep your kidneys warm, then you stop freezing! After improvising with shawls and scarves wrapped around my middle- fine if you're at home studying, not so practical at work or when out and about- I was delighted to find Nukunuku's haramaki as a Nice Way to keep your kidneys warm and not look like a womble.
Learning more about traditional Chinese medicine confirmed the importance of keeping your kidneys warm, and I tell my qigong students often that they should do this, especially living here in Sweden.
I bought a 'starter pack' with three haramaki in cheerful colours. I am now ordering my second set, as after four solid years of non stop use the first set have only finally been consigned, very reluctantly, to the rag bag. I wore and washed them constantly, and it was only after three or so years that they started getting a little saggy, with a hole here and there, but still completely useable. Quite remarkable considering the constant usage. 
Nukunuku's haramaki are well made, extremely durable, and comfortably combine with just about anything. I tend mainly to wear mine either as a first layer, or more often than not, over a singlet. The thickness is just right to be worn as a base layer without bulkiness. They are nice enough to be worn over things as well. The only reason I tend not to is that I am on the borderline between sizes, where the next size up is too big, but the size I use doesn't have a lot of leeway to allow it to be pulled over the top of layers.
Get some- it is SO worth it. They'll last you for ages and will make a difference to both your comfort and health. Be warned though, you will become dependent- I'm almost like a child without their teddy if I don't have a haramaki!!

The Washing Machine Post: Haramaki
20 May 2018
At its most basic level, the layering system consists of a base-layer, mid-layer and, every bit as importantly, the outer layer. it's a system that evolved principally for those enamoured with the great outdoors and there are more than a few companies or individuals who claim to have 'invented' it. however, since pretty much every outdoor clothing purveyor adheres to its benefits, the originator matters little. well, other than whoever did invent it, of course.

Though I've no doubt there will be those clamouring to disagree, the average cyclist suffers from breathability/perspirational issues to a greater extent than those who trek across great wastelands, or bag a couple of munros at the weekend. therefore, though the layering system applies every bit as much to the velocipedinally inclined, it's possible that clothing apportioned to the latter, may need the occasional tweek here or there. and it's no real secret that the holy grail for both, is the fabrication of a breathable outer-layer that is breathable enough for a cyclist making his or her way to the summit of the monte zoncolan in twenty-degree heat in the rain.
based on current technology, that grail is still some way off.
it may possibly be, however, that we are looking the wrong way. a few years past, development of the outer layer took a slight diversion, admitting that ultimately, it could not maintain total waterproofing indefinitely; eventually, any coated, waterproof fabric, cannot shed precipitation faster than it is being absorbed. that's when we get wet. accepting that to be a currently unsolvable fact, the clever money started looking at the likelihood of creating a material that would keep the individual comfortable even when wet.
look back to milan-sanremo around five years ago, and take note of the jacket favoured even by those sponsored by other manufacturers. that jacket was/is not 100% waterproof, but it hides that fact well until you reach the finish line.
but how comfortable we remain, if that outer layer features even a modest level of thermal properties, might well depend on our choice of base-layer. this mostly consists, at present, of the highly comfortable and distinctly non-aromatic merino wool version and the various polyester versions; offer a choice between both and i figure you'd probably have two lines of equal length standing in front of you. but ultimately, it's maintaining a stable core temperature when riding in cold weather that is the most important aspect. there's no real point in remaining dry, if hypothermia gets to you first.
The Japanese word haramaki, means 'belly-wrap, a stretchy cotton tube that is worn around the stomach and purports to maintain warmth in the face of adversity. i'd be loathe to wear one without matching it with a base-layer of some sort, if only for reasons of upper body comfort, but it pretty much seems to do what it says on the tin. though many will purport that wearing a base-layer of thicker material would surely offer the same benefits, that would likely risk serious overheating under strenuous conditions. back to the zoncolan summit once more.

The haramaki, available in several colour variants, is thin enough not to have your hard won svelte physique resemble that of billy bunter and, according to the distributors, is suitable for activities other than just cycling, something that could also legitimately be said about base-layers too. those months that encompass the spring classics are ideal for this item, as are those in the depths of mid-winter. once on, it's comfortable and stretchy enough to all but forget its existence, though it's worth my pointing out that, on a day that started cold, but heated up, my six-pack became a tad warmer than i'd prefer.
However, assuming, like me, you wear it over your bibshorts or bibtights, it's a relatively simple process to divest yourself of its benefits and stuff it in a back pocket. i'm not sure that i see it becoming a staple in the active cyclist's sock drawer; it's perhaps better suited to the commuting or leisure cyclist during the colder months, since they're less likely to benefit from the almost hermetic sealing of a clothing groupset. but at £12.50 each, it's definitely worth investigating for next winter.

The Bonnie Gardener 26.4.18  full blog post: "Haramaki - the key to staying warm while gardening"

"Last week I wore my new Haramaki out on a few chilly days (I live in Scotland, and we have barely emerged from Winter here). I wore it around my tummy and allowed the band to come over the top of the waist of my trousers (that way I got to show off the lovely bright pink colour).   The other way of wearing it is to tuck it into the top of the trousers, for minimal chance of draftiness.  I have to say throughout the day of gardening I felt incredibly cosy and noticed a huge difference compared to wearing only my normal gardening attire.  It was amazing the change I felt having my core area warm and with no draft around my midrift.   For those of you who garden, you will no doubt notice when you bend over to weed or pick up leaves, there can often be a gappy area between the trousers and the bottom of the t-shirt – well the Haramaki puts an end to that!"

Etsy Reviews - 5 stars 

"Another order of haramaki, so I can stay toasty all Winter. Thanks for the speedy dispatch" Nov 2017

"Brilliant Haramaki, just what i need to keep my back and kidneys happy. Ideal for gardening and Im loving mine so much I don't want to take it off! Helpful shop, quality item" Nov 2017

Hide your muffin top - with a waist warmer
Daily Mail 9 Feb 2017

"Do you have a favourite blouse that won't quite tuck into your sensible work trousers or a much-loved pair of jeans that now leave an unsightly muffin top on show? Its a perenial problem - that little gap over your midriff that threatens to appear whenever you sit down or bend forward. It might be wise to invest a waist warmer, the latest clever invention to disguise and flatter your middle. Also known as a haramaki, literally 'belly wrap' in Japanese, its a cloth tube that fits around your middle...."

For full article

Warm Kidneys on the Menu
Anna Murphy Fashion Editor in The Times 2 Dec 2015

"It's fair to say that kidneys don't exactly loom large in the British psyche. Unless they come accompanied with chunks of steak and topped with pastry....but in other cultures kidneys - of the human variety, that is - are seen as a key factor in remaining healthy. In traditional Chinese medicine the kidneys are considered to be the body's main energy storehouse. What is important above all, apparently, is that your kidneys are kept warm. In Japan there is even a special item of clothing for this very purpose, a haramaki, or belly wrap. 
In fact, we in the UK used to be more kidney-aware than we are now. During the Second World War, for example, extra fabric was added to British army shirts specifically to protect soldiers' kidneys from the cold. 
Last winter I tracked down a British company that makes its own version of the haramaki in user friendly pull-on cotton Lycra, no wrapping required (£12.50 Its great to layer under your Christmas dress to keep that annual Boxing Day proto-pregnancy extra snug"

Build Your Core Heat with a Haramaki
Kate Codrington 4 Nov 2013

"...this brilliant invention is a tube of jersey which enclosed the body from navel to thigh and actually feels like and all day hug. Its a think layer of clothing that you can wear under or over your clothes, and when I put it on I had that wonderful melting relaxation feeling you get when you're enfolded into someone's arms. Ahh. Now, I am tall and chilly and often have a drafty gap between my jeans and t-shirt and this perfectly fits the bill as a draft excluder. AND it encases my muffin tops if you know what I mean. "

Full blog post

Gabi Cox
Gift of the Gab 18 Oct 2013

"It is like having an extra warm layer across your middle...I have used a support band before, provided by one of the ostomy care companies- and this belly band beats that one hands down..."

Full blog post

Tips for wellbeing - cover up and keep your belly warm
6 Feb 2013
Avni Trivedi

"This winter I have been raving about wearing a haramaki. Its a traditional Japanese cotton productthat is worn around the belly and it has many benefits. Energetically it supports the kidneys which is essential for maintaining warm. If you're like me and don't like wearing too many bulky layers its a great way of keeping comfortable in the cold weather. For women it helps blood flow to the uterus, which is helpful for menstrual issues, pregnancy and postnatally. It can even be worn at night to ensure you drift away to a good night's sleep"

Its Fridaaaaaay! Time to get Waisted. 
All the Tall Things
9 Dec 2012

"Top won't stretch far enough? Maybe you need a Haramaki...They're useful for layering under a shrunken if clothes weren't short enough to start with, my washing machine is always determined to make things even shorter. If you're pregnant, slip one of these over the top of your Topshop skinnies and no one will guess that your flies have been undone forthe past nine months. They're also perfect for hiding that mince-pie and mulled wine induced muffin top. Me likey." 

Full blog post

9 Reasons to wear a Haramaki....
James Gisby, Acupuncturist Blog
5 Dec 2011

..."I've been wearing a haramaki for the last week. It fits unobtrusively under clothing and can be worn by both men and women, even in pregnancy. I found it to be surprisingly comfortable, giving a nice warm feeling over the low abdomen, reminding me of the awareness and warmth of the dan tian I used to have when I practiced a lot of tai chi and qigong. I walk a lot and found it to be a welcome extra layer of clothing"

Full blog post