The "Oh no" in the headline is for more than when things go wrong. It's specifically for that unsettling feeling that dries your mouth, tightens your throat, and flips your stomach after you logically correct a wrong and somehow make it worse.

At the start of what's been dubbed the Obesity Epidemic, the news of unprecedented weight gain was unwelcome in the U.S., but hardly cause for alarm. Logic dictated what had to be done.We had to eat less. We had to do more.But the eat-less-do-more strategy wasn't employed properly. Who can forget the fat-free eating craze that essentially swapped fat for bleached flour and added sugar? Or the 30-minute weightlifting workouts for women that didn't build but "tone" muscle?Changes like these didn't reverse the trend. They escalated it. And rather rapidly.Here's where the oh-no feeling should've kicked in. Especially when you consider 18- to 29-year-olds.With the benefit of youth and relatively fast metabolisms, you'd expect this age group to have a relatively easy time losing weight. Before the epidemic began, 29 percent of 18- to 29-year-old Americans were overweight. Yet by 2005, 25 years into the epidemic, the rate had risen to 52.1 percent.Adding fuel to the oh-no feeling: the rate of overweight 12- to 17-year olds more than tripled during the same time. Prior to this alarming increase, generally the opposite occurred. Puberty would so supercharge the metabolism that growing teens burned off the childhood chubbiness euphemistically called baby fat, not add to it.And don't forget the most frequently cited oh-no statistic. By 2005, two out of every three American adults were overweight.From the theories created to explain such troubling weight gain, a second sort of oh-no feeling emerged. The one where you realize the problem is due, at least in part, to conveniences so ingrained in the culture that you couldn't imagine giving them up.Automobiles. Elevators. Riding mowers. Leaf blowers. Snow blowers. As well as dozens of other devices around the house and the workplace that minimize your manual labor.The processed foods that keep you out of the kitchen. The irresistible technology that keeps your eyes on a screen and your back side in a chair for much of the day.So how do you retain the lifestyle without gaining unwanted body weight?You update. You recognize that the eat-less-do-more strategy was right on but that a myriad of factors can make it go wrong. One of those that we knew relatively little about in the 1980s is epigenetics.Epigenetics can be hard to understand, so let's liken it to your personality. Different, difficult or demanding situations reveal different parts of your personality. These situations don't really change your personality; however, they do move certain elements of it to the forefront.Similarly, external influences can modify your genes without really changing them. The results of these modifications and the study of them are called epigenetics.A sleep study published in Clinical Endocrinology and Metabolism this summer sheds light on how external influences may be modifying your genes to create weight gain. Swedish researchers at Uppsala University and the Karolinska Institute manipulated the normal sleeping patterns of 15 healthy normal-weight men and found that even a one night's disruption created epigenetic changes that make weight gain (and type 2 diabetes) more likely.The study consisted two separate sessions of nearly two days' length. In each session one night's sleep was slightly over eight hours, but the other night's sleep didn't really include any sleep at all. The subjects spent slightly over eight hours in bed but were never permitted to fall asleep.Tissue samples taken from the subjects' stomach fat and thigh muscles during these sessions revealed chemical alterations during the sleep deprivation that affected genetic expression. In other words, one night's loss of sleep was impaired insulin sensitivity, which leads to weight gain (and ultimately type 2 diabetes).Other studies have found epigenetics to be not as immediate but generational.One 12-year study published this July in Cell Metabolism undernourished a group of rats for 50 generations while properly nourishing a control group for the same time. The next two generations of both groups were then fed the original, control-group diet that kept 50 generations of rats at a normal weight.But the two generations of rats whose ancestors had been undernourished did more than reach a normal weight. They exceeded it to such a degree that, when compared to the control group, they were eight times more likely to develop diabetes.So what are you to take from this column? That external influences, like a lack of sleep or your ethnic makeup, may negate the weight loss that you expect from a reduction in calories and an increase in exercise.So if you're diligent about eating right and working out and you're still not at the weight you desire, try increasing the amount of sleep you get.And if you're a bit overweight and your ancestors were impoverished, your body still might be geared not to waste energy, especially the type derived from simple carbohydrates. In that case, a diet high in protein that replaces virtually all simple carbohydrates with complex ones deserves an attempt.