What will keep you warmer?

Ever wondered if fleece was toastier than wool, or soup more warming than curry? We asked the boffins about what’s hot and what’s not.

A hot drink or a bath?

Definitely a hot bath, says Mike Tipton, Professor of Human Physiology at the University of Portsmouth. ‘The only way to truly warm up is to keep core body temperature (that of your vital organs) at about 37°C. Immersing yourself in a hot bath (around 41°C) is one of the most effective ways of doing this. A massive 75 per cent of our body’s heat is lost through our skin’s surface into air, but in water there’s nowhere for that heat to go – it circulates back to the core again. You can raise your temperature by 1°C in just 15 minutes in the tub.’ Having a hot drink, however, is just a drop in the ocean of body warmth. ‘Your body is made up of 66 per cent water at a temperature of 37°C – diluting it with one cup of tea really isn’t going to make a difference,’ says Mike.

Feathers or synthetics?

‘Natural products are always warmer,’ says Lucy Warwick, bedding buyer at John Lewis. ‘Our quilts contain feathers from ducks and geese living in some of the coldest places on earth – and the chillier their habitat, the warmer their feathers. They’ve naturally evolved to cope in harsh temperatures, mostly owing to the thick, fluffy down next to their skin. Feather quilts are warmer than synthetic ones, but down quilts are warmer still.’ A standard duckdown double duvet at John Lewis costs £75. A synthetic quilt will do the job if you opt for a microfibre polyester version, which contains tiny fibres to trap body heat. A double duvet will cost you from £60.

Gloves or mittens?

Just look at the mittened hands of any Arctic explorer for the answer. Mike explains why: ‘In order to protect our vital organs, the body sacrifices the extremities by switching off blood flow (and therefore heat) to them. That’s why we feel the cold most in our fingers and toes. To make matters worse, our fingers and thumbs are like ten cylinders with a large surface area from which heat can escape. By wearing mittens instead of gloves, you’re decreasing that area (two cylinders instead of ten), so losing less warmth.’

Soup or curry?

Eating any kind of food warms you up slightly because you’re giving your digestive system a metabolic workout – and exercise generates heat. But curry offers a double-whammy internal heating effect thanks to the capsaicin contained in chillies. Scientists at the University of California recently discovered that a person’s food-induced heat production was significantly increased for several hours after eating a spicy meal. Vindaloo, anyone?

Fleece or wool?

Fleece may be high-tech, but old-fashioned wool wins out. ‘Merino wool is particularly good at regulating temperature. It has an impressive warmth-to-weight ratio compared to synthetics and to other wools, because the fibres are smaller and hairier, so have more spaces in which body heat can be trapped,’ says Tim Jasper, brand director for outdoor specialist Rohan. ‘If you’re opting for fleece, go for hollow fibre over microfibre, as this has been shown to retain body heat for longer. Add an outer layer of windproof clothing to reduce the chill factor.’

The pub or the gym?

Despite the rosy glow a tipple can bring, exercise is better. ‘Alcohol increases blood flow to the skin, and while you may feel hotter as it hits your heat sensors there, your body is actually losing its warmth,’ says Mike. ‘Exercise is a good way of cranking up your internal thermometer because the process generates heat. In fact, on a brisk walk, our bodies produce the same amount of warmth as a one-bar fire.’ But wear layered clothing and a hat to stop that heat escaping.

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