6. Do I cut calories or fat to lose weight?
Cut both for best results. "It is a lot easier to restrict calories when you cut fat, while cutting fat aids in weight loss only if it is accompanied by a drop in calories," Brownell explains. The National Weight Control Registry -- an ongoing project at the University of Pittsburgh and the University of Colorado -- found that dieters who maintained a 30-pound or more weight loss for more than one year were successful in part by limiting their calories to about 1,300 a day and keeping fat to about 24 percent of calories.
7. Do calories from saturated fat take longer to burn than calories from unsaturated fats?
Probably not. A handful of studies, mostly on animals, found that the monounsaturated fats in nuts and olives might burn a little faster than saturated fats. "All fats are metabolized differently, but the differences are so slight that switching from one fat to another has no practical use for weight loss," Foreyt says. Of course, the fats from most plants and fish are heart-healthy, so that benefit alone is good reason to switch from filet mignon and butter to fillet of sole and olive oil.
8. Are "empty" and "hidden" calories the same thing?
No. Empty calories describes foods that offer little or no nutritional value. For example, for 112 calories, an 8-ounce glass of fresh-squeezed orange juice offers potassium and supplies 100 percent of your daily need for vitamin C, while the same amount of orange soda has 120 calories and is completely devoid of nutrients. The soda delivers empty calories; the OJ does not. In general, the more a food is processed, the lower its number of vitamins, minerals, fiber and cancer-fighting agents known as phytochemicals, and the higher its content of fat, sugar and empty calories.
In contrast, hidden calories can be found in all types of foods. These are the calories that sneak into your diet quietly, such as from the butter added to vegetables in a restaurant kitchen. "If you eat away from home, you're in for trouble, because you don't know how many hidden calories from fat have been added to your meal," Foreyt warns.
The easiest way to avoid hidden calories is to ask about ingredients whenever someone else has prepared your meal and to request that food you're served at restaurants be steamed, baked or broiled dry. When purchasing packaged foods, always check the nutrition label. That seemingly harmless bran muffin could harbor several grams of fat, upping the calorie content significantly.
9. Do no-calorie foods aid in weight loss?
Theoretically, yes. Switch your daily cola to diet cola and you'll save about 160 calories per 12-ounce can, which should lead to about a 17-pound weight loss over the course of a year. However, scientists have learned that when people consume lowfat, sugar-reduced, low-calorie or calorie-free foods, they typically compensate by eating more of something else later. A Pennsylvania State University study of women found that those who were told they were snacking on reduced-fat yogurt ate more food at their midday meal than did women told the yogurt was full-fat, regardless of the actual fat content of the snack.
To make no- and low-calorie foods work to your advantage, use them in combination with tried-and-true habits for permanent weight loss, such as reducing portion sizes, getting at least 25 grams of fiber a day, eating lots of fruits and vegetables and exercising five times a week.
10. Do calories eaten at night act differently from those eaten during the day?
Not really. "Eat a huge dinner or snack uncontrollably in the evening and there might be a slight fat-storing effect compared with eating a big breakfast followed by a physically active day," Foreyt says. "But the effect is so insignificant that it won't have any noticeable influence on your weight." However, for most of us, dinner typically is the biggest meal of the day, supplying almost half of a person's daily caloric intake, and that's not even counting a late-night snack of ice cream or chips. Bigger portions and excess calories at any time of the day will pack on the pounds. Significant research shows that eating a nutritious, low-calorie breakfast -- for example, a bowl of whole-grain cereal topped with fruit and nonfat milk -- makes it easier to manage your weight. That's not because of any difference in how the calories are burned, but because you're less likely to overeat later in the day if you start off with a healthful meal.