We all know what hunger feels like: The empty, loudly protesting stomach; the can’t-think-about-anything-but-food lack of concentration; the need-to-lie-down low energy; and that infamous irritability commonly known as hanger. But what causes it? What makes it worse? And what can you do to keep it away? Grab a sandwich (or a handful of almonds) and find out.

Woman eating

What is hunger?

Being hungry can be annoying, but it’s your body’s well-meaning way of letting you know that the tank is running low. “Hunger is a biological necessity and sensation, and is very much hormonally regulated, and in its pure form depends mainly on internal cues,” explains Dr. Ivanka Nikolova, PhD, Head of Health Research at RunRepeat.com. Note that this is in contrast to appetite. “In general, appetite is what we’re hungry for, and sometimes doesn’t relate to hunger at all,” Dr. Nikolova adds. “We all sometimes just want to eat something, even though we’re not hungry. Appetite is a matter of preference and socialization, and largely depends on external cues.” So hunger is that feeling of “I’ll eat anything!” and appetite is craving the cupcake your colleague is eating — even though you’ve just had lunch.

What causes hunger?

While your appetite can be stirred by something external, like walking past a bakery, the mechanisms that cause hunger work internally and are largely controlled by hormones. Amanda Perrin, MS, an LA-based registered dietician who runs nutrition website Purely Perrin, did her Masters thesis in satiety hormones. “Ghrelin and leptin are just two of the many hormones that help regulate our hunger and satiety. Ghrelin is released from the stomach when our bodies are physically hungry, and is sent to our brain to say, ‘Hey, it’s time to eat.’ Leptin is the opposite. After we eat, certain macronutrients release different hormones, including leptin, to tell our brain that we are full and we don’t need to eat anymore,” she says. “Leptin is released from adipose tissue. When leptin is high, ghrelin is low, and vice versa. They work both autonomously and synergistically to help maintain energy balance.”

It does get a bit more complicated than the double-team efforts of ghrelin and leptin. “There are also many other hormones like CCK, PYY, GLP-1, and GIP that all work in conjunction with leptin to tell our brains that we are full,” Perrin elaborates. “CCK, GLP-1, and GIP work by delaying gastric emptying — slowing down the food going from the stomach to your small intestine, keeping you fuller longer — while PYY sends signals to your brain saying you are full, and helps maintain that feeling until the next meal.”

What affects hunger?

What you do with your body also affects this process, in sometimes surprising ways. For starters, not getting enough sleep can wreak havoc on your hormones. “Sleep deprivation can cause low levels of leptin and high levels of ghrelin, which can lead to overeating or choosing higher sugar or more processed foods the following days,” Perrin warns. “Sleep is one of the most important things you can do if you are trying to lose weight, be active, relieve stress, or just get into a healthy lifestyle.”

What you eat can also play into how hungry you feel and when it hits you. “Certain hormones respond to certain macronutrients — specifically carbs, fat, and protein — so having a balance of these at each meal helps ensure each of these hormones is released and that they can do their jobs,” explains Perrin. “I tell my clients to always have the ‘Pure Four’ at each meal: Greens/veggies, protein, fiber, and fat. This keeps your glucose levels stable so there isn’t going to be a spike of insulin followed by a dramatic drop [which can cause cravings for simple carbohydrates] and slows down the time it takes for the food to leave your stomach.”

In particular, she focuses on fat. “It plays a really crucial role,” she says. “Fat is the macronutrient that most increases the secretion of PYY. When this hormone is circulating in the blood, it keeps telling the brain that you’re full and don’t need any more food.” We’re not talking just any kind of fat, though. “Polyunsaturated fats, found in foods like salmon, flaxseeds, pumpkin seeds, hemp seeds, and almonds, have been shown to have the greatest effect on PYY, so make sure those are present in your meals,” Perrin advises.

Can you work up an appetite?

Appetite may be distinct from hunger, but it plays a big role in when and what we choose to eat. “The sight and especially the smell of foods make us hungry faster,” Nikolova says. As for the phrase “work up an appetite,” it might be true — but only because you haven’t fueled up properly beforehand. “If you didn’t eat before working out, your blood sugar can be low,” Perrin warns. “This causes the release of a hormone called glucagon, which leads to you feeling hungry and needing to eat.”

It might also be that you’re dehydrated. “Try drinking more water and see if that alleviates the feeling of extreme hunger post-workout,” she says. And it also depends on what you’re doing, and how your body works. “Workouts like running for 30 minutes could make you hungrier than 30 minutes of higher intensity workouts,” she suggests. “Each person is different though, so if you go do a barre class with a friend and you are famished after and they aren’t, that’s okay.”

What’s your best hunger-beating recipe? Share it with us @BritandCo.

(Photo via Getty)