“Hunger is not as simple as needing food to meet physical needs,” says Aner Tal, a research associate at Cornell University’s Food & Brand Lab. “There are many different psychological and biological and environmental factors that affect hunger.”
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Not least of which are your eating habits, Tal says. “If you’re used to eating lunch every day at 2 o’clock, you’ll feel the need to eat at 2 o’clock even if you don’t have a biological requirement for food at that time,” he says. Eat all the time, and your body will slowly learn to expect food—and crave it—all day every day.
But what causes you to eat all the time in the first place? Your food choices play a big part in that, says Dr. Belinda Lennerz, an endocrinologist and researcher at Boston Children’s Hospital and Harvard Medical School.
“The fundamental role of hunger is to drive us to seek and consume food in order to keep the amount of available energy in our blood stable,” says Lennerz, who has conducted research into the dietary drivers of hunger and cravings. “This occurs more effectively when we consume a meal higher in fat, protein and fiber, which are digested slowly.”
While these foods help our bodies achieve and maintain a satisfyingly balanced state for hours between meals, others foods trigger metabolic shifts that send us back to the kitchen or snack room much sooner after we’ve eaten, Lennerz says. You can probably guess what foods she’s talking about: highly processed carbs.
Dr. David Ludwig—Lennerz’s colleague and co-researcher at Harvard and Boston Children’s and author of the recent book Always Hungry?—calls out many of the most popular processed carbs by name: white bread, white rice, potato products, sugar-sweetened beverages, prepared breakfast cereals, cookies and chips. "These foods confuse your body’s natural hunger-control systems, which usually work really well when you’re eating slowly digesting foods," he says.
Unlike healthy fat- and fiber-rich foods—the Greek yogurts and leafy green vegetables and legumes that calmly stroll through your digestive system—processed carbs move through your gut like it’s a Slip’N Slide.
These snack foods, sweets, sugary drinks and other processed goodies make up 61% of average American shopping cart. And your body’s reaction to these quick-digesting foods is to release large amounts of insulin into your bloodstream in order to normalize your surging blood sugar levels, Lennerz explains.
Like a cattle rancher, insulin herds sugar and the other calories from your meal into storage, which usually means your fat cells, Ludwig says. This not only promotes weight gain, but it also tricks your body into believing you need more energy to satisfy your body’s needs, which in turn causes your hunger to rebound rapidly. If you also happen to be on a low-fat diet high in processed foods, all of this is intensified, Ludwig says.
It's not easy to avoid, of course. “In today’s food environment, food is readily available without a delay at any given time,” Lennerz says. She adds that merely smelling or seeing food can fire up your brain and body’s “feed me” processes. That means watching TV shows about cooking, seeing snacks on your kitchen counter or walking by a break room where cookies or chips are on offer can all stoke hunger pangs that would have remained dormant if you hadn’t been exposed to those temptations.
Add to this the growing body of research that shows many of these highly processed foods—particularly sugar—can fire up our brains’ reward systems in ways similar to cigarettes, drugs and other addictive substances, and it’s no wonder many of us spend our days with a case of the munchies.
So what can you do about it? For starters, ditch those highly processed foods in favor of the healthy, fatty, fiber and protein-rich foods Lennerz and Ludwig mentioned above. Research suggests mindfulness meditation, a brisk walk, exercise and keeping food out of sight can also help knock down your incessant cravings.