What's the official word on letting your mouth stray beyond the breakfast-lunch-dinner circuit? Scientists have yet to figure it out.
For one, snacking is tough to study. Try giving volunteers their meals in a controlled lab setting, and they don't eat close to how they would normally. Ask them to try to remember what they ate yesterday in the real world, and they'll likely be way off in their reports -- either because they don't remember or because they don't want to remember.
There are always the easier-to-study rats, of course. But when it comes to nutrition, we're just not rodents. Rats are surprisingly determined to keep up healthy habits -- including watching calories. Sure, they'll accept snacks, but then they'll eat less rat chow later on.
Studies have shown that humans haven't learned that trick. Give us potato chips during the day, and we'll gratefully scarf them down -- and then go on to eat a full dinner at night. (Scientists aren't sure why we do this -- or, more important, how to get us to stop.)
One thing is clear: Snacking is still eating. So if you're going to snack, here are some thoughts about how to do it more wisely.
* Don't underestimate how junk food messes with normal willpower. "Our body appears to be good at regulating our food intake when only healthy foods are available," says Kelly Brownell, director of Yale's Rudd Center for Food Policy & Obesity. "But once you introduce high-fat, high-calorie foods, all bets are off. Foods high in sugar, fat and calories appear to throw off the body's normal regulatory ability."
A 2005 study at Penn State University found a high-fat diet might dampen normal responses to "stop-eating" chemicals in the gut. Rats fed high-fat chow for normal meals reacted abnormally to a hormone called cholecystokinin -- also found in humans -- which triggers feelings of fullness and helps the brain to decide when to stop eating. Rats fed high-fat chow ended up ignoring the signals and ate 40% more high-calorie snacks than normal-chow rats.
The upshot (if this experiment were to apply similarly in humans): If your everyday diet is high in fat, your normal appetite signals might have gone awry, leaving you more susceptible to snacking urges that others can more easily resist.
* Try reprogramming yourself. "You can, in fact, change your tastes and expectations," says Margo Wootan, nutrition policy director at the Center for Science in the Public Interest. "If you're used to eating fruits and vegetables for snacks, that's what you'll begin to crave. Save the Doritos and the cookies for a real treat instead."
