"Radical changes are necessary," says Deirdre Barrett, a psychologist at Harvard Medical School and author of Waistland. "People don't lose weight by choosing the small fries or taking a little walk every other day." Barrett suggests taking a cue from the members of the National Weight Control Registry (NWCR), a self-selected group of more than 5,000 successful weight-losers who have shed an average of 66 pounds and kept it off 5.5 years. Some registry members lost weight using low-carb diets; some went low-fat; others eliminated refined foods. Some did it on their own; others relied on counseling. But when it came to keeping weight off over the long term, they had one thing in common: vigorous exercise for at least an hour most days of the week. Most also participated in at least one other activity or sport. "People in the NWCR exercise a lot," says Barrett. She estimates they burn an extra 2,800 calories a week.
That said, not everyone can lose 66 pounds and not everyone needs to. The goal shouldn't be getting thin, but getting healthy. It's enough to whittle your weight down to the low end of your set range, says Jeffrey Friedman, a geneticist at Rockefeller University. Losing even 10 pounds vastly decreases your risk of diabetes, heart disease, and high blood pressure. The point is to not give up just because you don't look like a swimsuit model. "We focus on appearance because that's what everyone notices," says Friedman. "If there were no stigma, we wouldn't be worried about an unachievable goal. We'd just be worried about our health."
The Womb: Go Ahead, Blame Your Mother
The negotiation between your genes and the environment begins on day one. Your optimal weight, writ by genes, appears to get edited early on by conditions even before birth, inside the womb. If a woman has high blood-sugar levels while she's pregnant, her children are more likely to be overweight or obese, according to a study of almost 10,000 mother-child pairs.
Maternal diabetes may influence a child's obesity risk through a process called metabolic imprinting, says Teresa Hillier, an endocrinologist with Kaiser Permanente's Center for Health Research and the study's lead author. The mother's high blood sugar may mean the baby in the womb gets overfed, possibly pre-programming it for obesity. Even mothers whose blood sugar was at the upper end of the normal range had elevated risks of having overweight babies. The good news is that high blood sugar during pregnancy, known as gestational diabetes, is entirely avoidable: Children born to women who sought treatment for diabetes during pregnancy ended up no fatter than their peers.
The implication is clear: Weight may be established very early on, and obesity largely passed from mother to child. Numerous studies in both animals and humans have shown that a mother's obesity directly increases her child's risk for weight gain.
The best advice for moms-to-be: Get fit before you get pregnant. You'll reduce your risk of complications during pregnancy and increase your chances of having a normal-weight child. But if you think you're still at risk for gestational diabetes, make sure you get screened for hyperglycemia during pregnancy. If your blood sugar is high, talk to your doctor about treating it by modifying your diet and exercise. If that doesn't work, your doctor may prescribe insulin.
Insulin: The Great Diet Bake-Off
It's the $64,000 question: Which diets work? A yearlong government-funded study comparing Atkins, the Zone, Ornish, and LEARN (Lifestyle, Exercise, Attitudes, Relationships and Nutrition, based on the U.S. government's food pyramid) found all four work more or less, leading to short-term modest weight loss in overweight women. People on Atkins lost the most weight—an average of about 10 pounds—while participants on the other diets lost between 3.5 to 5.7 pounds on average.
Not exactly huge numbers. It got people wondering: Isn't there a better way to diet? Two months later another study seemed to offer an answer. The paper compared two groups of adults: those who, after eating, secreted high levels of insulin, a hormone that sweeps blood sugar out of the bloodstream and promotes its storage as fat, and those who secreted less. Within each group, half were put on a low-fat diet and half on a low-glycemic-load diet.
On average, the low-insulin-secreting group fared the same on both diets, losing nearly 10 pounds in the first six months—but they gained about half of it back by the end of the 18-month study. The high-insulin group didn't do as well on the low-fat plan, losing about 4.5 pounds, and gaining back more than half by the end.
But the most successful were the high-insulin-secretors on the low-glycemic-load diet. They lost nearly 13 pounds and kept it off. Their diet was designed to mitigate swings in blood sugar by replacing easily digested simple carbs—white bread, potatoes, fruit juice, cookies, and other refined foods—with vegetables, low-sugar fruits, and legumes.
Why were they so successful? The hormone insulin, which is secreted by the pancreas, is like a natural appetite suppressant. It's released when blood sugar rises, and it signals the brain that it's time to stop eating. When blood sugar and insulin drop too quickly, the brain takes it as a signal that it's time to feed, and so people feel hungry again sooner after eating—leading to overeating and weight gain.
How does your own insulin response measure up? Only a blood test can tell you for sure, but in general, low-secretors tend to be pear-shaped, carrying excess fat around the hips; high-secretors are apple-shaped, storing flab around the midsection.
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