The Real Influences on Your Weight

Exercise and dieting aside, behavior and biology appear to have a real influence on weight gain

Eating When You Should be Asleep & Other Weight-Loss Saboteurs

We're a country obsessed with being thin, yet two thirds of American adults -- and nearly one third of children and adolescents -- are overweight or obese and either suffering from or at risk of serious chronic illnesses like diabetes and heart disease. Ironic, given the thriving weight-loss industry that seems to churn out a new diet book or fat-loss pill every other week. Even when dieters do succeed at slimming down, research has found that the majority end up gaining back their losses.

What gives? Yes, weight loss depends largely on getting the balance right between calories consumed and calories burned. Yet, as evidenced by individuals' struggle to control weight and also by the nation's alarmingly increased rate of overweight and obese residents in recent decades, mastering this seemingly simple formula is no small task. Willpower alone probably won't do the job, since several sneaky factors may be complicating the equation. Here are a few that may be working against your efforts to control your own weight.

Eating very late at night. Snacking at times that are out of sync with your circadian clock might be promoting weight gain. Researchers at Northwestern University's Center for Sleep and Circadian Biology, who just published new evidence in the journal Obesity, were inspired by earlier studies suggesting that irregular eating habits caused certain groups of people to be overweight: shift workers awake and eating at night; people who skip breakfast; and people with night-eating syndrome, who get a large percentage of their daily caloric intake after the dinner hour and regularly wake up and go foraging in the middle of the night.

To investigate whether late-night eating might translate into more pounds than daytime eating, the Northwestern team forced a group of mice to flip their normal wake-sleep schedule and allowed them to eat a high-fat diet only when they'd normally be asleep. Compared to a control group that ate a high-fat diet during regular waking hours, these out-of-whack mice gained significantly more weight. "I think sleep has a very important role in metabolism," says Deanna Arble, a neuroscientist at Northwestern and the lead study author. She thinks the research may have implications for humans as well as mice: "For someone not consuming excess calories each day, and they're doing everything by the book but still gain weight, maybe look into the time of day you're eating. It could be a factor," she advises. But the new research "does not mean you can eat as much as you want because it's the right time of day."

Taking in too much added sugar. The highly processed American diet is packed with added sugars and syrups, which quickly translate into a whole mess of trouble. The American Heart Association, concerned that excessive sugar intake may be linked to metabolic abnormalities and poor health and also crowd out healthful nutrients in one's diet, has just suggested a daily upper limit -- that women get no more than 100 calories from added sugars and men no more than 150. At the moment, the average daily intake is 22.2 teaspoons, or 355 calories. The top culprits, notes the AHA, are soda and other sugary beverages like fruit juices and sports drinks. But even seemingly healthful dried, sweetened cranberries and reduced-fat or reduced-calorie salad dressings contain high levels of added sugar, for example.