Hungry for more

Several of my co-vegans during this vegan challenge have told me that they’ve been hungrier than usual since going vegan. I agree with them, vegan food makes me hungrier too, although I see that as a perk letting me eat more often. So why is this? I decided to learn more about what it is that makes us hungry and what makes us feel full, and how our appetite works. And just like with anything else that involves the human body, it is more complex than you’d think.

Before going any further it’s important to define the difference between these terms, hunger, appetite, satiety. Hunger is a physical need for food, our bodies’ way to tell us they need more energy or nutrients. Appetite on the other hand is the psychological desire to have food. It’s related to our behavior and can be triggered by for example seeing or smelling something delicious. Finally, satiety is the body’s way to tell us to stop eating, that it has what it needs for now.

Hunger is a complex thing. Scientist long believed that the only thing controlling our feeling of hunger was the contraction of the stomach. One scientist went as far as to swallowing a balloon connected to a tube to prove this. As long as the balloon was inflated, he felt no hunger. Yet this theory doesn’t hold in the long run, as even people who have had to have their stomachs removed will feel hunger. The body can also signal hunger when its glucose levels are too low as well as due to psychological factors. I know I just said hunger was physiological rather than psychological, but sometimes our minds can play tricks on us. Hunger can be affected by the mental state we’re in, for example if we are stressed. It can also be a learned response, a habit, triggered by our biological clock. You might have experienced that you are hungry for lunch at the same time every day, independent of what you’ve been doing.

How soon we become hungry after eating is largely dependent on our metabolism. The metabolism is the breaking down of food to energy that is needed to sustain the body, even when resting. Different people do this at different rates and need different amounts of energy in their resting state. This is determined by several factors such as gender, age, hormones and muscle mass. More muscles require more energy, even when they’re not active.

At some point after eating, we will become full and not want to eat any more. When this happens is depends on several different factors. The most obvious one of these is the actual volume of the food we consume. The food will stretch our stomach. When eating a large meal, it may have to expand from the size of a fist to a volume of 2 liters. There are masses of nerves in our stomach, and when this stretch happens, they will send signals to our brain telling it we’ve gotten something to eat. These are not the only signals being sent to the brain though. As the stomach is being emptied, the hormone ghelin is produced. When we eat this production lessens, which is also signaled to the brain. It doesn’t end there. Further down in our intestine, in the ileum, another hormone, PYY, is produced once the food as passed through the stomach. This hormone tells the brain to tell us that we are full. You might have heard that it takes 20 minutes to know if you’re full or not, and that is because it takes the food 20 minutes to reach the ileum.

When we eat hormones such as lectin and insulin are produced and they as well can tell the brain that we’ve eaten. They interact with dopamine-producing neurons in the hypothalamus of the brain. This changes the levels of dopamine in the brains reward center, and thereby determines if we want to eat more or not. The hypothalamus is thus the part of the brain controlling our appetite. Appetite is also affected by outside influences, such as colors and images. Seeing a yellow banana can make us hungry. Seeing a red banana on the other hand probably won’t. This is because we are programmed to want to eat natural things that we know are safe to eat. Red bananas are not natural. This is why the color blue is believed inhibit appetite, because few natural, edible things are blue.

So how does vegan food connect to all of this? Why does a vegan diet make many of us hungrier? Well, the main reason is that a vegan diet often consists of foods with a high saturating power but a lower energy content. The saturating power is basically how full a food will make us feel. Proteins, fibers and water have a high saturating power, whilst fat has a low. A vegan diet is often high in fiber, making it more filling. Think about eating a big bowl of kale for example. It is rich in fiber making us feel satiated, but the pure bulk of it will also make us feel full. Still a bowl of kale does not contain a whole lot of calories. After a while the body will realize that even though it thought it had gotten all the energy it needed, it had merely been filled up with a bowl of kale. As our bodies require a certain amount of energy, no matter what we do, it will then tell us to eat more. A vegan diet often not as dense in calories, and we therefore have to eat larger volumes of food to get the energy we need.

If you feel that a vegan diet is making you hungrier, simply make sure to have some good filling snacks around. I must say it suits me very well, since I've always been a good snacker. I rarely say no to a reason to have more food. Keeping some fruit, nuts, good energy bars or a sandwich in your bag or at home might be a good thing, if you find yourself suddenly hungry.