Why Brown Fat May Be the Key to Weight Loss

4 minute read

Not all fats we eat are created equal. We all know that, trying to dodge the less healthy ones that come from animals and dairy products and load up on those less likely to clog our arteries and add to our waistlines.

But it turns out that even after we consume fat, we store it in different forms as well, and scientists reporting in the journal Cell have identified a pathway in the brain that can direct our bodies to convert stubborn waistline-growing fat into a different fat that’s easier to burn off.

MORE: Having The Right Kind of Fat Can Protect Against Diabetes, Study Says

Brown fat, so-called because it is rich in the darker hued energy factories of cells known as mitochondria, is a calorie-hungry machine. It consumes a lot of energy and generates just as much, mostly in the form of heat. That’s why brown fat is more common in newborns, who need to be protected from getting chilled after nine months in the toasty womb. As we age and are better able to regulate our body temperature, we lose brown fat, and until recently scientists thought most adults had little brown fat, if any.

Now researchers at Yale School of Medicine have identified the process that turns white fat, the more common kind in the average adult body and the primary culprit in weight gain, into the energy-consuming brown fat.

QUIZ: Should You Eat This or That?

Which is better for you: A 1/2 cup of ice cream or 3 scoops of sorbet?
Which is better for you: Half cup of ice cream or 3 scoops of sorbet?Getty Images (4)
Answer: A 1/2 cup of ice cream
Answer: A half cup of ice cream If you eat what you’re craving, you’re more likely to feel satisfied and eat less. And scoop for scoop sorbet contains twice the sugar with none of the filling dairy protein and fat.Getty Images (5); Gif by Mia Tramz for TIME
Which is better for you: Real butter or spray on fake butter?
Which is better for you: Real butter or spray on fake butter?Getty Images; Tara Johnson for TIME
Answer: Butter
Answer: Butter Serving size for spray butters (even low-calorie ones) are around a 1/3 second spray. What on earth does that mean? You're better off using a small amount of real butter as opposed to guessing how much you're using of the mystery melange of up to 20 ingredients.Getty Images (1); Gif by Mia Tramz for TIME
Which is better for you: A sirloin burger or a turkey burger?
Which is better for you: A turkey burger or a sirloin burger?Getty Images (2)
Answer: Sirloin burger Restaurant turkey burgers are often made with dark meat and the skin, so they’re not necessarily better for you (and for the record, they aren't low-fat). You can get a sirloin burger that’s 95% lean meat and gives you 20 g of protein. Just be careful with the toppings.Getty Images (1); Gif by Mia Tramz for TIME
Which is better for you: Almonds or pretzels?
Which is better for you: Almonds or pretzels?Getty Images (2)
Answer: Almonds
Answer: Almonds Almonds are high in protein, fiber and fat and will keep you feeling fuller longer. Give high-sodium pretzels about an hour and you'll feel hungry again thanks to the high-carb no-fat or protein content.Getty Images (1); Gif by Mia Tramz for TIME
Which is better for you: Eggs or Special K?
Which is better for you: Special K or eggs?AP; Getty Images
Answer: Eggs
Answer: Eggs In the morning, you want a meal that will fill you up. Eggs offer protein and fat for satiety, but Special K cereal really only offers carbs and, well, air. If you want carbs to kick off the day, you're better off pairing eggs with a slice of 100% whole grain toast. Getty Images (1); Gif by Mia Tramz for TIME
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Which is better for you: Fat free salad dressing or regular salad dressing?Tara Johnson for TIME
Answer: Regular salad dressing
Answer: Regular salad dressingTo absorb fat soluble vitamins like Vitamins E and K in vegetables you need to consume them with a fat to aid nutrient absorption. Fat-free dressing, meanwhile, is low-calorie but gets its flavor from added sugar and salt.Tara Johnson for TIME (5); Gif by Mia Tramz for TIME
Which is better for you: A low fat cookie or dark chocolate?
Which is better for you: A low fat cookie or dark chocolate?Getty Images (2)
Answer: Dark chocolate “People tend to believe fat free is calorie free,” says Keri Gans, a registered dietitian in New York City. “Go for the real thing.” Fat free cookies may be lower in fat, but higher in other ingredients like sugar. Try a nice piece of dark chocolate for those antioxidants.
Answer: Dark chocolate “People believe fat free is calorie free,” says Keri Gans, a registered dietitian in New York City. “Go for the real thing.” Fat free cookies tend to be high in carbs, sugar and fake sugar. Try a nice piece of antioxidant-rich dark chocolate instead.Getty Images (2); Gif by Mia Tramz for TIME
Which is better for you: Low fat Greek yogurt or 100 calorie Yoplait yogurt?
Which is better for you: Low fat Greek yogurt or 100 calorie Yoplait yogurt?Tara Johnson for TIME
Answer: Low fat Greek Yogurt
Answer: 2% Greek YogurtA little fat is good in the morning to keep you full—plus it has upwards of 17g of protein per container. Fat-free "fruit" yogurt is high in sugar—7 to 10 g per serving—and lower in protein.Tara Johnson for TIME (2); Gif by Mia Tramz for TIME

MORE: How Now, Brown Fat? Scientists Are Onto a New Way to Lose Weight

Working with mice, the scientists honed in on a set of neurons in the brain that regulate the body’s energy balance, including the breakdown of glucose, which is the primary source of fuel for most cells. When mice fast, for example, their bodies shift into a type of emergency mode, conserving energy and shutting off systems and cells that require high amounts of energy, such as the heat-generating brown fat cells. Fasting resembles times of starvation, so evolutionarily, this makes sense; when food is scarce, the body shunts its energy toward essential processes, such as keeping the heart pumping and getting oxygen to the brain.

Xiaoyong Yang, an associate professor of comparative medicine and physiology at Yale, showed that this switch to conserve energy is intimately tied to hunger signals in the brain. “We showed that hunger itself is a signal that controls the browning of white fat, so the brain can actually control the browning of white fat.”

That means it’s the brain that regulates what type of fat, and how much of it, is burned. In obese animals, Yang found, these hunger signals are dysfunction; overweight and obese mice eat regardless of whether they are hungry, so the normal physical signals from the stomach don’t function properly. Heavier animals continuously feel hungry, even if they’ve eaten enough for their energy needs. That perpetuates the cycle of obesity, since it shuts off the transformation of white fat into energy-consuming brown fat, and therefore keeps more fat in an inert, pound-packing form.

“Obese animals, and people, lose the response to hunger,” he says. “Although there is plenty of food and plenty of energy, the hunger neurons send a false message that the body needs to conserve energy, not burn it.”

Eventually, he says, it might be possible to intervene with the hunger signal anywhere along its journey from the brain to the fat cells, and that may shift the balance in favor of burning fat rather than storing it, which might open the door to weight loss. But calibrating the switch will be critical, since favoring the burning of fat can also lead to other physiological problems such as wasting and malnutrition. “You don’t want to set the body’s energy balance to zero,” says Yang. “You want to reset it to normal levels.”

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