Can you freeze your fat away?

Can you ice your way to a slimmer body? New products and procedures keep popping up, promising to help you do just that. Intuitively, the idea makes sense: The colder you get, the more your body has to work to heat itself up, and that extra effort should burn calories.

A study out this month boosted the theory with a tantalizing hint that cold could help spur weight loss by changing the microbiome (at least in mice).

But should you strap an ice pack around your waist? Probably not. Scientists say that’s unlikely to help you shed pounds all over.

The science behind freezing your fat away

Fat cells come in colors, so to speak. White fat tissue stockpiles fat to keep your body’s energy up, and is the most abundant type of fat in your body. Brown fat cells burn calories to generate heat and keep body temperature stable. (They’re darker in color thanks to an increased presence of mitochondria — the tiny organelles that generate the energy cells need.)

Fat-freezing techniques specifically target brown fat.

Researchers at the University of Geneva, for instance, exposed mice to cold temperatures for up to 10 days. That exposure changed the composition of bacteria in the animals’ guts. The scientists then transplanted the new brew of gut microbes into other mice, which didn’t have any microbes of their own.

The recipient mice formed more brown fat — and lost weight.

The technique has its limits. The mice exposed to cold did lose weight, but only for a few weeks. After that, their weight stabilized as they began to absorb more nutrients from their foods. But the research, published this month in Cell, suggested that harnessing the way cold changes the microbes in your body — and, consequently, the way you metabolize food — could be a potential avenue for fighting obesity.

Body sculpted by cold

While scientists fiddle with mice, entrepreneurs have rushed to promote cold as a weight loss tool.

You can have your fat frozen by a medical professional in a procedure called cryolipolysis. Approved by the FDA in 2010, the technique uses a machine to cool fat deposits to a chilly 40 degrees.

The idea — which the controversial TV showman Dr. Mehmet Oz has touted as a way to “revolutionize the fight against fat” — aims to kill off the fat cells just under your skin. Over the next few months, the body naturally removes those dead cells. But the cold only kills cells in the area treated, so it’s not ideal for reducing overall body fat.

The procedure is often marketed under the brand name CoolSculpting and costs range from $750 to $1,500 a pop depending on how much fat you want to target.

Fat freezing can cause bruising and numbness that can last for a prolonged period, experts said, but it’s less invasive than liposuction, the traditional surgical procedure that uses suction to reduce fat. The downside: “They’re not one-shot deals. You might have to do them two, three, four times,” said Dr. Murad Alam, a Northwestern surgeon who conducted a review of the comparative effectiveness of various fat reduction techniques.

A vest packed with ice

For those who want DIY fat freezing, options abound.

There’s the Fat Freezing Wrap — basically a giant ice pack that you wrap around your waist.

Or consider the Cold Shoulder Vest, which aims to lower your body temperature so you burn more fat to stay warm. A crowdfunding campaign on the website Kickstarter brought in 2,000 orders of the “semi-fashionable” vest, said Wayne Hayes, a computer scientist turned entrepreneur, who invented the product.

He recently released version 2.0, made with a glycerin-based ice that lasts longer, so you can wear the vest for several hours before needing to stick it back in the freezer.

The vest got a fair amount of press this fall. But it doesn’t have much science behind it. Hayes, an associate professor at the University of California, Irvine, said the only test he’s run was asking four fitness buffs to wear the vests for two weeks.

“We are currently planning to do a much larger clinical trial that’s more independent than me just testing it on some gym rats,” he said.

Dr. Philip Kern, a University of Kentucky endocrinologist who has studied the effects of cold exposure on fat, said he isn’t sure an icy vest will burn calories any place beside the abdomen, where it’s exposing the body to cold. He said there’s still a lot of research to be done on the effects of cold. “It’s possible that different areas of our body respond differently to cold,” he said. 

Of course, if you want to use the power of the deep freeze to stay trim this winter, there are other ways to do it than buying a $200 vest packed with ice. There’s skiing. Skating. Walking outside in the brisk air. Or this:

“We all know intuitively that cold weather boosts your metabolism,” Kern said. “If you live in Green Bay and roll around in the snow naked every Sunday, that’s good stimulus for burning fat.”