Eating When You Should be Asleep (and 3 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.

[Check out a list of foods surprisingly high in added sugar.]

Not getting sufficient sleep. The lower people dip below seven hours a night, the fatter they seem to become. A theory about why: The intricate dance between hunger hormones appears to be disrupted when a person clocks too little shut-eye; for example, leptin, which suppresses appetite, is lowered while ghrelin, which stimulates appetite, gets a boost. According to a 2006 Institute of Medicine report that reviewed the body of research on sleep, "Addressing obesity will likely benefit sleep disorders, and treating sleep deprivation and sleep disorders may benefit individuals with obesity."