October 10, 2014
News Review from Harvard Medical School - Cold Temperatures Change Fat Behavior
Body fat can burn more calories in colder temperatures, a study has found. The study examined belly fat in 55 people. Samples were taken in the summer and winter. Belly fat is generally considered to be white fat, which does not burn many calories. But the winter belly fat behaved more like brown fat, which burns calories at a higher rate. Babies have high levels of brown fat, which is believed to help keep them warm. The study also had people put ice packs on their thighs for 30 minutes. The fat underneath the ice pack was then examined. It was expressing genes that are active in brown fat, but not white fat. These effects were limited in obese people, however. Researchers are interested in finding other ways to make white fat behave more like brown fat. This could lead to treatments for obesity, or prevention strategies. The study was published Oct. 9 in the online version of the Journal of Clinical Endocrinology and Metabolism. TIME and U.S. News and World Report wrote about it.
By Howard Lewine, M.D. Harvard Medical School
What Is the Doctor's Reaction?All fat is not created equal. It turns out there is good fat and bad fat.
The typical fat we think about is called white fat. It's the kind that isn't good for you. It stores calories and adds inches to waist lines.
The other kind of fat called brown fat does the opposite. It creates heat and burns calories, which can lead to weight loss.
Newborn babies have a relatively high amount of brown fat. As we age, we lose much of our brown fat and white fat increases. Most adults have more than 1,000 times more white fat than brown fat.
We can't naturally make our bodies produce more brown fat. But this study and other research shows that white fat can be stimulated to act more like brown fat.
Cooling white fat turns on a couple of genes that increase the metabolic activity of fat cells. The fat cells begin to burn more calories. Scientists have coined the term 'beige fat' for this transformed white fat.
But not everyone has the same potential to make white fat behave more like brown fat. People that are obese don't have the same response to fat cooling. Their white fat doesn't become beige.
What Changes Can I Make Now?Right now you still need to rely on the basic weight loss formula. You need to burn more calories with physical activity than you take in.
Most recently I have been recommending a reduced-calorie, Mediterranean-style diet:
Five or more servings of vegetables a day. A serving is ½ cup of raw or cooked vegetables, 1 cup of raw leafy greens or ½ cup of vegetable juice. Four servings of fruit a day. A serving is ½ cup of fresh, frozen or canned fruit; ¼ cup of dried fruit; one medium-sized piece of fruit; or ½ cup of fruit juice. About 3 tablespoons of olive oil a day. One handful (about 1½ ounces) of nuts, 3 times per week. Three to five servings of legumes (beans, peas and lentils) per week. A serving is ½ cup. Five servings of whole grains a day. A serving is 1 cup of dry breakfast cereal; ½ cup of cooked cereal, brown rice or whole-grain pasta; or one slice of whole-grain or multi-grain bread. Three or more servings of fish (especially fatty fish) a week. A serving is 4 ounces. One serving of yogurt or cheese a day. If you enjoy alcohol, limit yourself to an average of one drink a day. One drink is 5 ounces of wine, 12 ounces of beer or 1½ ounces of liquor.
Specifically avoid:
Soda and sugary drinks Sweets, pastries and commercial bakery goods Red and processed meats (eat white meats instead) Margarines and most tub spreads
What Can I Expect Looking to the Future?Keeping your house cooler won't become the new trend to lose weight. Our bodies adjust to lower temperatures in other ways. So at most you might shed a pound or two by turning down your thermostat. It's still a good idea if you want to save money on heating bills.
But scientists are likely to get excited about this study. If cool temperatures can alter white fat to act more like brown fat, it raises the possibility that there are other ways to create more beige fat.
