Steven Blair is, in his own words, a “short, fat, bald guy.” But at five-foot-five and 200 pounds, he may very well be healthier than men much taller and leaner. He runs 25 miles a week, eats six to eight servings of fruits and vegetables a day, and avoids processed and fatty foods. A professor of exercise science and epidemiology at the University of South Carolina, Blair is a living example of how fat doesn’t play fair. And thanks to advances in his field, he is beginning to understand why.
Genes, hormonal imbalances, and even viruses are now acknowledged to play a role in obesity. Eating less and working out more, in fact, don’t have nearly as much to do with weight loss as you might assume. “This is all counter to what people think they know,” says Blair. “You can see obesity, so it’s easy to say ‘Well, that person must not be trying. He must be lazy.’ But that’s often not the case.”
Our team pored over the latest studies, interviewed the top clinicians in obesity science, and listened to the real-life experiences of men and women struggling to maintain their weight. Here, the latest (and often unexpected) thinking behind size and thighs, fatness and fitness.
1. It Really Is Genetic
When scientists first discovered it in certain chubby mice, they called it simply the fatso gene. Years later, when they scoured the human genome for markers that increased vulnerability to type 2 diabetes, the fatso gene (now more politely called FTO) showed up there too. Turns out, people with two copies of the gene were 40 percent more likely to have diabetes and 60 percent more likely to be obese than those without it. Those with only one copy of the gene weighed more too.
Scientists now suspect that there are lots of fat genes. “There could be as many as 100 of them,” says Claude Bouchard, PhD, executive director of the Pennington Biomedical Research Center at Louisiana State University System, “each adding a couple of pounds here and a pound or two there. That’s a noticeable difference when it comes to how much more fat we need to burn off.”
As much as 16 percent of the population has two copies of the FTO gene, and half of us have one copy. So far, scientists suspect that the other possible obesity-promoting genes have a small effect compared with FTO. The good news? “A genetic predisposition isn’t necessarily a life sentence,” says Bouchard. Exercising regularly can offset the risk.
2. Some People Just Have More Fat Cells
And the range is enormous, with some people having twice as many fat cells as others have, says Kirsty Spalding, PhD, of the Karolinska Institute in Stockholm. Even if you’ve lost a few pounds (or gained some), your fat-cell count remains, holding tight to the fat already inside and forever thirsting to be filled up with more. (To add insult to injury, the fat cells of overweight and obese people hold more fat too.)
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New fat cells emerge during childhood but seem to stop by adolescence. Those of us destined to have a lot of these cells probably start producing them as young as age two. The cells’ rate of growth may be faster, too—even if kids cut way back on calories.
Strangers have written to Spalding, telling her how depressed they are by her research. But she says her news isn’t all bleak. You’re better off with more fat cells, she says, than with fewer fat cells that become overstuffed and enlarged. (New research suggests that the overstuffed group are more vulnerable to obesity-related health complications.) So while you can’t reduce your total number of fat cells, there are things you can do to keep them small. (See next point.)
3. You Can Change Your Metabolism
Another Scandinavian team looked into what happens at the cellular level when you gain weight. Kirsi Pietiläinen, PhD, an assistant professor of nutrition at Helsinki University Central Hospital, studied sets of twins where one was fat and the other thin, and learned that fat cells in heavier twins underwent metabolic changes that make it more difficult to burn fat. Pietiläinen’s team suspects that gaining as little as 11 pounds can slow metabolism and send you spiraling into a vicious cycle: As you gain more fat, it becomes harder to lose it.
How to get back on track? “The more I learn on the job, the more I’m convinced we need physical activity,” Pietiläinen says. Once a chubby child herself, she now runs regularly and is at a healthy weight.
4. Stress Fattens You Up
The most direct route is the food-in-mouth syndrome: Stressful circumstances (your bank account, your boss) spark cravings for carbohydrate-rich snack foods, which in turn calm stress hormones. (When researchers in one study took away high-carb food from stressed mice, their stress hormones surged.)
Stress hormones also ramp up fat storage. For our prehistoric ancestors, stress meant drought or approaching tigers, and a rapid-storage process made sense; we needed the extra energy to survive food shortages or do battle. Today we take our stress sitting down—and the unused calories accumulate in our midsection.
To whittle yourself back down to size, in addition to your usual workout routine, make time for stress relief—whether it’s a yoga class or quality time with family.
5. Mom’s Pregnancy Sealed Your Fate
A mother’s cigarettes increase the risk of low birth weight, and alcohol can damage her baby’s brain. So why wouldn’t unhealthy foods wreak similar havoc? A growing body of science suggests that sugary and fatty foods, consumed even before you’re born, do exactly that. A Pennington study on rodents reports that overweight females have higher levels of glucose and free fatty acids floating around in the womb than normal-weight ones do. These molecules trigger the release of proteins that can upset the appetite-control and metabolic systems in the developing brain.
What’s true for mice is often true for humans too. Doctors from State University of New York Downstate Medical Center compared children born before their mothers had gastric bypass surgery with siblings born later. Women weighed less after the surgery, as expected, but their children were also half as likely to be obese. Because siblings have such similar genetic profiles, the researchers attributed the weight differences to changes in the womb environment. Moms-to-be, take note: You can give your kids a head start by eating well before they’re born.
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6. Sleep More, Lose More
When patients see Louis Aronne, MD, past president of the Obesity Society and author of the forthcoming book The Skinny, they’re as likely to have their sleep assessed as their eating habits. If patients are getting less than seven to eight hours, Dr. Aronne may prescribe more shut-eye rather than the latest diet or drug. With more sleep, he says, “they have a greater sense of fullness, and they’ll spontaneously lose weight.”
Why? University of Chicago researchers reported that sleep deprivation upsets our hormone balance, triggering both a decrease in leptin (which helps you feel full) and an increase of ghrelin (which triggers hunger). As a result, we think we’re hungry even though we aren’t—and so we eat. Indeed, sleep may be the cheapest and easiest obesity treatment there is.
7. Your Spouse’s Weight Matters
When Jodi Dixon’s six-foot-two, 360-pound husband lost 125 pounds, she had mixed feelings. She was the one who always watched her weight and exercised; she was always the one trying to get her husband to be more active. Mort, a medical sales rep, was always the life of the party, says his wife, a 43-year-old mother of two in Freehold, New Jersey. But when he lost the weight, it was different.
“Men and women would flock to him, drawn to his charisma,” she recalls. “I felt jealous.” Dixon comforted herself with food and gained 20 pounds before she decided to take action. She began biking with her husband and enrolled in a diet program. Eventually she trimmed down, too, shedding 30 pounds, and has her sights on losing more.
Dixon credits the weight gain, and the loss, to her jealousy. But research shows that weight gain and loss can be, well, contagious. A study in the New England Journal of Medicine suggests that if one spouse is obese, the other is 37 percent more likely to become obese too. The researchers concluded that obesity seems to spread through social networks.
As in Dixon’s case, slimming down seems to be catching, at least within the family: When Dixon launched her weight-loss plan, her eldest daughter, also overweight, followed her mom’s healthy habits and lost 40 pounds.
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