Why am I Hungry?
How does your body know it is hungry? What does hunger mean? These are important questions to understand how your body normally regulates hunger.
Hunger is a sensation that represents the physiological need to eat food. This sensation typically manifests after only a few hours without eating and is generally considered to be unpleasant. Satiety is in contrast with hunger, it is the absence of hunger, the sensation of feeling full. Appetite is experienced with eating, the desire to eat food.
An interesting fact: A healthy, well-nourished individual can survive for weeks (from 3 to 10 weeks) without food intake.
Basically our sense of hunger tells us when our body is running out of fuel, stored energy in the cells. All of this information is based on communication within our body by hormones.
Let’s see a few of them.
Insulin is released from the beta cells of the pancreas, regulating blood sugar, aging and body fat and its primary role as nutrient sensor. It puts nutrients into our cells, however insulin plays a very important role in many other processes completely unrelated to blood sugar management.
Why is blood sugar or blood glucose so important? Certain parts of our brain and the red blood cells can run only on fuel like glucose. BUT it does not mean we need to eat tons of carbohydrates because it is much better for our body if it runs on fat as fuel and we provide just enough carbs to meet the needs of the glucose dependent tissues.
If we reduce the body’s need for carbs we protect ourselves from blood sugar crashes.
Glucagon is the counter-hormone of insulin and it is stimulated by hunger (decreased blood glucose level), increased amino acid level and CCK (cholecystokinin hormone).
Glucagon and insulin help us to manage energy levels by releasing and storing nutrients.
This hormone stimulates hunger and makes you eat more when you are stressed and/or have lack of sleep because these two factors can increase ghrelin levels. If you want to keep a lean body and lower body fat % adequate sleep is very important.
4. Peptide YY
PYY tells us when we need to stop eating. This hormone is highly released when you eat protein and fat so the sensation of hunger disappears faster. If you eat lots of carbs much less PYY is released which is why a cereal or muffin or waffle with honey breakfast leaves you ravenous in a few hours.
Leptin is the hormone that tells our body how much fuel we have and when we are full. It controls appetite and metabolism. If it works properly it will tell you when we have enough food and we are full.
When we lose the ability to sense this hormone, appetite control is lost and you can eat and eat and eat and you will overeat all the time. This can lead to obesity, cancer, accelerated aging, neurological degeneration. Why? Not because of this hormone only but many others too. If one hormone does not work correctly in your body the others that are related to leptin will not work properly either.
This hormone also tells us when we are full and it also has an important role in our system. It protects the arteries from oxidative damage. It correlates with the body fat so people with low body fat % have high level of adiponectin.
Cortisol raises blood glucose level and this can cause fat gain mostly around the midsection. It has a more common name: “stress hormone” because it is released when you are stressed, but this is just one reason of an increased level of cortisol. Other causes are lack of sleep, caffein. Yes my friends, caffein – coffee, tea, etc.
This hormone can be and is our friend. Why? Because it is a crucial anti-inflammatory, but we do not need too much of it.
I rather call this hormone as a “survival hormone” because if we go back to the era of our hunter-gatherer ancestors and there were great dangers – e.g. chased by a raptor – their cortisol level increased quickly leading to increased levels of blood glucose which led to a quick released energy for the body so they had the chance to escape.
The only difference between them and us, modern people, is the period of time they had increased cortisol level. Normally the level of this hormone is decreasing and going back to the normal level when the danger is gone.
In our modern days the stress hormone can be high all day thanks to our boss, colleagues, financial situation, family, lack of sleep, drinking coffee all day to keep you “alive”, etc.
The mechanism of getting hungry
Let’s start with the fact you are full.
1. Leptin level is high so you have the sensation of being full
2. After hours of non-eating the level of leptin is dropping
3. Ghrelin (the counter hormone of leptin) is increasing so you will feel hunger again
As I mentioned earlier a lot of hormones play a big role here. During eating insulin and cholecystokinin(CCK) are also released from the gastrointestinal tract and act to suppress the feeling of hunger.
Our body is a very well built system because through the vagal nerve fibers our brain can sense a difference between different macronutrients. So the level of macronutrients also has an effect on feeling hungry.
Also, levels of blood glucose, amino and fatty acids provide a constant flow of information to the brain that may be linked to regulating hunger and energy intake. Nutrient signals that indicate fullness and therefore inhibit hunger include the following:
– Rising blood glucose levels
– Elevated blood levels of amino acids
– Blood concentrations of fatty acids
Here I would like to talk a little about the Glycemic-index. It is important because you might have just finished two slices of cake and an hour later you feel hungry again. However, your body is full.
This index shows that the type of food (carbohydrate) you consume how much and how fast increases blood sugar levels.
You can find a chart below and you can also browse on the internet for more.
The ranking is usually up to 100 where sugar (glucose)=100
Foods below 50-55 have a low index so they are slower to digest so they increase blood sugar levels slower and later they keep the elevated glucose level more stable and slow dropping.
Foods above 65-70 are the opposite. Quick absorbing carbs increase the blood sugar fast and this level drops quick and fast so you will be hungry however your stomach is still full and digesting the meal from two hours ago.
Factors that may affect the GI of a food include: (source)
– Cooking methods: frying, boiling and baking.
– Processing and the ripeness of fruit and certain vegetables.
– Whole grains and high fibre foods act as a physical barrier to slow down absorption of carbohydrate. This is not the same as ‘wholemeal’, where, even though the whole of the grain is included, it has been ground up instead of left whole. So some mixed grain breads that include whole grains have a lower GI than either wholemeal or white bread.
– Fat lowers the GI of a food. For example chocolate has a medium GI because of its fat content and crisps will actually have a lower GI than potatoes cooked without fat.
– Protein lowers the GI of food.
– Milk and other dairy products have a low GI because of their high protein content and because they contain fat.
Please note that your diet and meals do not have to depend on the glycemic-index only. It must be balanced and rich in nutrients.
It is not the end of the world if you eat high GI foods sometimes but definitely eat more low or medium GI ones. Keeping balance is the key.
Read more articles like these on Richard Csosza’s Expert Profile.