If you've ever eaten a sugary bowl of cereal or a couple of doughnuts, you've probably realized about an hour or so later, you're hungry again. There are certain foods that simply don't satiate because they don't have the nutrition to keep your body fueled.

The science behind what makes us stay fuller longer — or rather what makes the brain send signals that tell us we're full — is still in its research phase. A recent study by The University of Warwick in the U.K. isolated key brain cells that control appetite.

Researchers found that brain cells called tanycytes tell the brain you feel full when they detect two specific amino acids in foods — arginine and lysine. Foods that have these amino acids include pork shoulder, beef sirloin steak, chicken, mackerel, plums, apricots, avocados, lentils and almonds. In theory, eating these foods should trigger satiety and we should feel fuller longer when eating them.

With this discovery, researchers are looking at the possibility of finding a way to trigger tanycytes in the brain to help suppress appetite and therefore help control weight. But that doesn't help us now if we're trying to eat healthy foods that will fill us up so we can eat less overall.

Fortunately, we can eat foods with tanycytes as well as foods that are high in fiber, protein and carbohydrates that are known to help us feel full longer. If you're looking to eat a satiating breakfast to keep you full until lunch, skip the sugary cereal and the doughnuts and add these foods into your morning routine.

Raspberries

A woman holds a bowls of raspberries Raspberries have a surprisingly high amount of fiber in them. (Photo: GrashAlex/Shutterstock)

Because of the volume of water and fiber in fruits, one serving can last a long time. There's a surprisingly high amount of fiber packed into a cup of raspberries: 8 grams. When foods contain water, air or fiber, they "cause the stomach to stretch and empty slowly," according to WebMD. This helps you feel fuller longer.

You'd have to eat two servings of apples (with their skins), bananas, oranges or strawberries to get the same amount of fiber as you do in raspberries. They each have only 3 to 4 grams of fiber in a serving.

Yogurt

A bowl of yogurt with mixed berries A bowl of high-protein yogurt plus some high-fiber berries will go a long in way keeping your stomach free from hunger pangs. (Photo: Ozgur Coskun/Shutterstock)

Not all yogurt is created equal. When choosing yogurt to help you feel fuller longer, skip the sweet varieties that can contain as much sugar as ice cream and go for plain, high-fiber yogurt like Greek or Icelandic Skyr yogurt. One cup of Siggis plain, zero percent milk fat Icelandic Skyr yogurt contains 28 grams of protein and 10 grams of carbohydrates while containing only 150 calories. To add a little sweetness to the sugar-free yogurt, pile some high-fiber berries on top.

According to Forbes, when scientists studied the eating habits of people who did and did not gain weight as they aged, yogurt was the food most associated with keeping weight off. This could possibly be because the probiotics in yogurt promote healthy gut flora, or it just could be because health-conscious people tend to eat yogurt.

Avocado

Avocado and eggs on toast Adding avocados to your breakfast can help keep you full until lunch. (Photo: Anastasia Izofatova/Shutterstock)

You may be eating avocados at breakfast already, and if you are, it's a very smart and tasty idea. A 2014 study funded by the Haas Avocado Board (so keep in mind it's industry-sponsored) found that eating one-half of a fresh avocado at lunch made people less likely to want to eat after the meal. Those who ate half an avocado had a 40 percent decreased desire to eat in the next three hours and a 28 percent decreased interest within the next five hours.

It's not much of a stretch to think that if the study is accurate, the same results would hold true when avocado is eaten at breakfast, too. Try mashing it on toast and topping it with an egg like above, or make sweet potato toast to top with the avocado and egg.

Oatmeal

oatmeal Can a daily dose of oatmeal keep you fuller untill lunch? (Photo: Viktor1/Shutterstock)

A 2013 study on oatmeal found that a 250-calorie serving of oatmeal that was high in fiber and low in sugar — meaning plain oats, not the ready-to-eat sweetened packets or microwavable cups — kept people fuller than a same-calorie serving of ready-to-eat cold cereal.

This doesn't mean you have to eat just plain oatmeal, though. You can add berries, nuts or sugar-free nut butters to your oatmeal to flavor it without adding a lot of sugar. For those with little time in the morning, overnight oats made with ingredients like Greek yogurt, berries and nut butters are ready to eat as soon as you wake up.

Pistachios

pistachios It may seem counterintuitive, but pistachios can help you lose weight. (Photo: Handmade Pictures/Shutterstock)

Pistachios are nutrition powerhouses with more than 30 different vitamins, minerals and phytonutrients, but that's not the main reason they're also a satiating addition to a meal. One 1/4 cup serving (about 49 nuts) contains 6 grams of protein and a little over 3 grams of fiber. And, while these nuts are high in fat, it's the heart-healthy kind of fat. The pistachios can be eaten alone, or they're a great addition to other satisfying foods like yogurt or oatmeal.

Keeping the pistachio shells where you can see them after you've eaten them may be an added way to keep hunger at bay, too, according to U.S. News and World Report. One study found that when people left the shells on their desk, they ate 18 percent fewer calories than those who threw them away. The shells may have been a reminder of how much was eaten, making it less tempting to eat more.

One last piece of advice: No matter what food you're eating, eat mindfully. Pay attention to the fact that you are eating — not just mindlessly shoveling food in your mouth as you do other tasks. It's another way to help you eat less because you're aware that you're eating.

Robin Shreeves ( @rshreeves ) focuses on food from a family perspective from her home base in New Jersey.