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Make Over Your Metabolism—Really!

To burn more fat, avoid diabetes and keep your heart healthy, get in sync with your internal body clocks (there are more than you think)

by Arlene Weintraub
Photograph: Brian Stauffer

Anyone who has experienced jet lag knows about the body’s circadian clock. Operating on a 24-hour cycle, this cluster of neurons in the brain is stimulated by light and dark and, scientists say, controls the timing of various body processes, such as sleep and digestion. That’s why when we travel overseas we wake up at the wrong time and sometimes even feel ill: Our circadian clock has not yet shifted to the new time zone. But according to the latest research, that familiar clock is just one of many timing mechanisms in the body, and understanding them can be a key to our physical well-being.

These timing mechanisms, called clock genes, exist throughout the organs and tissues of the body and are not linked to the cycles of daylight and darkness. In a 24-hour cycle, they turn on and off at particular moments, governing essential metabolic processes such as the burning of fat. Sometimes they interact with the circadian clock in our brains, but they often operate independently.

In unlocking the mysteries of these genes, scientists are discovering strategies that make it easier for people to lose weight and potentially fend off killer conditions like diabetes and heart disease (mutations in certain clock genes have been linked to insomnia, obesity and an increased risk of cancer). Here are some goals you can achieve, based on what research has established so far.

Goal 1: Slim down faster
Clock-gene research suggests you can drop pounds simply by fiddling with the timing of your meals. For instance, in a Spanish study published last year, dieters who consumed their main meal before 3 pm lost about 5 percent more weight than those who ate later—even though both groups consumed the same number of calories (1,800 a day), says lead researcher Marta Garaulet, PhD, professor of physiology and nutrition at the University of Murcia.

Why would eating early create a calorie-burning advantage? It has long been known that some of the fat you ingest is used by the body and some of it is stored (typically in the thighs and abdomen). Researchers have now discovered that adipose (body fat) tissue has clock genes that flip on and off in a rhythmic pattern to discard excess fat—but these timekeeping genes shut down as the day wears on, so less fat is broken down and more is stored. It makes sense, then, that dieters who consume big meals late in the day won’t lose as much weight as those who eat earlier. “If you eat at the wrong time, you lessen the probability of breaking down fat stores in your body,” Garaulet says.

Research in Israel also backs the theory that you can boost weight loss by tapering your calorie intake throughout the day. Scientists at Hebrew University of Jerusalem and Tel Aviv University took two groups of obese women and gave them three meals a day for 12 weeks. All participants consumed the same number of calories, but half the women ate the highest-calorie meal in the morning and the other half at dinnertime. Those who ate a bigger breakfast and a smaller dinner lost more than twice as much weight as the others. “This again proves it’s not just the number of calories you consume that’s important; it’s also when you consume them,” says lead author Oren Froy, PhD, professor at the Institute of Biochemistry, Food Science and Nutrition at Hebrew University.

The advice to eat a big meal early in the day may be particularly useful for women, who, according to the latest research, are not nearly as good as men at metabolizing fat while they’re sleeping. This means women’s bodies are more likely to turn late-night meals into stored pounds. No one knows yet why women are different, says Vincent Cassone, PhD, chair of the department of biology at the University of Kentucky in Lexington.

First published in the April 2014 issue

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