Appetite and Eating Behaviour Regulation – Why Do We Eat Even When We’re Not Hungry?

Eating is not only about survival. Yes, food is the body’s main source of energy and nutrients needed to build and repair tissues. But eating is also emotional, social, comforting, and sometimes simply habitual.

We eat because food tastes good. We eat because it’s lunchtime. We eat because we’re stressed, bored, tired, or overwhelmed. And sometimes… we eat even when our body doesn’t truly need fuel.

So what is really happening inside the body when we feel hungry—or when we suddenly crave something sweet?

This article is part of my mini-series of articles on 'The Body, the Digestive System and Processes Influencing Appetite', where I share the knowledge that I have gained in my online course at Tallinn Health University of Applied Sciences. You can read my previous articles here:

• The Digestive System – a Remarkably Intelligent System Supporting Our Health Every Day

• How Nutrients Are Digested and Absorbed in the Body

• Diverse Nutrition and the Gut Microbiome – The Invisible Foundation of Health

Let’s take a closer look at how appetite is regulated.

Hunger vs. Appetite – Not the Same Thing

Hunger is a biological signal that your body needs energy and nutrients. Appetite, on the other hand, is more psychological and emotional. It is a learned motivation to eat, often triggered by external factors such as:

• the smell of food

• the sight of a favourite dessert

• taste memories

• social situations

• emotional states

For example, you may not be physically hungry, but the smell of freshly baked pastries or grilled meat can still create a strong desire to eat.

At the same time, a stressed or sick person may truly need nutrients, but feel no appetite at all.

The Brain Controls Eating More Than We Realise

The regulation of eating behaviour is controlled by a complex system involving the digestive tract, blood chemistry, hormones, and the brain.

The “feeding center” is located in several areas of the central nervous system, including:

• the hypothalamus

• the brainstem

• the limbic system (emotions and reward)

• the cerebral cortex (thinking and decision-making)

These brain areas receive signals from the body and decide whether we should start eating… or stop.

Why Do We Feel Hungry? Key Theories Explained Simply

Over the years, researchers have developed several theories about what triggers hunger.

1. The Glucostatic Theory (Blood Sugar Theory)

This theory suggests that hunger is triggered by a drop in blood glucose levels.

When blood sugar drops, the brain receives a signal:“We need fuel.”

After eating carbohydrates, insulin is released, glucose enters cells, and the brain receives a “safety” signal—leading to a feeling of satiety.

2. The Aminostatic Theory (Protein and Amino Acids)

This theory suggests that appetite is influenced by the level of amino acids in the blood.

After a protein-rich meal, amino acid levels rise and hunger tends to decrease.

This helps explain why protein often keeps us full longer.

3. The Lipostatic Theory (Body Fat and Long-Term Energy Storage)

This theory focuses on the role of fat tissue and leptin, a hormone produced mainly by fat cells.

Leptin acts as a long-term regulator of energy balance. When energy stores are sufficient, leptin sends a signal to the brain:

“We have enough stored energy—reduce appetite.”

When someone diets or loses weight, leptin levels drop, and the brain responds with increased hunger and cravings.

This is one of the reasons why long-term dieting can feel so difficult: the body is biologically designed to protect its energy reserves.

Interestingly, many overweight individuals have high leptin levels but suffer from leptin resistance—meaning the brain does not respond properly to leptin signals, similar to insulin resistance in type 2 diabetes.

4. The Thermostatic Theory (Body Temperature Theory)

This theory suggests that eating increases body temperature, and warmer blood affects the hypothalamus in a way that reduces appetite.

Although this theory exists, evidence is less strong compared to other appetite-regulating mechanisms.

Serotonin, Tryptophan, and the Craving for Carbohydrates

One of the most fascinating appetite-regulating factors is serotonin, a neurotransmitter strongly connected to mood, appetite, and satiety.

Serotonin production in the brain depends on the amino acid tryptophan, which we must get from food.

Here’s the important detail:

Why carbohydrates can influence serotonin

After eating carbohydrates, insulin levels rise. Insulin affects amino acid balance in the bloodstream in a way that may help tryptophan enter the brain more easily.

Once tryptophan reaches the brain, it can be converted into serotonin.

This helps explain why many people experience a calmer mood and reduced appetite after eating a balanced meal containing carbohydrates.

However, this does not mean consuming foods and drinks with added sugar (cakes, cookies, sweet pastries, ice-cream, candies, soft drinks etc) is the solution.

The best support for serotonin production comes from whole-food sources such as:

• whole grains (whole rye, barley, wheat, oat)

• legumes (lentils, beans)

• seeds and nuts

• vegetables and fruit

• foods rich in B vitamins (needed for serotonin synthesis).

  • You can find the foods containing different B-vitamins under my Resources page Vitamins one pager.

Serotonin and Sleep: The Melatonin Connection

Serotonin is also used to produce melatonin, the hormone responsible for sleep regulation.

That means good nutrition doesn’t only influence appetite and mood—it can also influence sleep quality.

Appetite and Seasons: Why Winter Can Feel Harder

Serotonin levels tend to be higher in summer and lower in winter, especially in Northern countries with limited sunlight.

This is one reason why many people:

• crave more carbohydrates in winter

• feel more tired

• experience mood drops or seasonal sadness

• find weight management harder during darker months

Sunlight has a powerful influence on mood and appetite regulation.

Leptin, Sleep, and Why Poor Sleep Increases Hunger

Leptin does not only respond to fat storage and energy balance—it is also affected by sleep.

Short sleep duration can reduce leptin levels and increase appetite.

Most adults need around 7–8 hours of sleep a night, although individual needs may vary.

Poor sleep is one of the most underestimated reasons why weight loss becomes difficult.

Ghrelin – The Hunger Hormone That Makes Dieting Hard

Another major appetite hormone is ghrelin, produced mainly in the stomach.

Ghrelin increases appetite and rises when we restrict food intake.

This is why low-calorie diets often lead to strong hunger signals: the body responds by producing more ghrelin.

Ghrelin is also connected to growth hormone release and energy regulation.

When we eat less, ghrelin rises. When we eat enough, ghrelin decreases.

Why Fullness Doesn’t Happen Immediately

Many people think fullness happens during a meal. But in reality:

true satiety often appears 60–90 minutes after eating. That is why eating too quickly can easily lead to overeating.

This is also why mindful eating habits matter:

• eat slowly

• chew well

• avoid distractions

• stop eating before feeling full

Eating in a calm environment supports digestion and satiety signals.

Long Gaps Between Meals Can Backfire

If someone eats very little during the day and then comes home extremely hungry, they are likely to eat too fast and too much.

This can lead to blood sugar spikes and increased insulin demand.

Over time, repeated patterns of overeating in the evening may contribute to insulin resistance and weight gain.

Regular meals with balanced macronutrients can help stabilise appetite and energy levels throughout the day.

So Why Do We Eat When We’re Not Hungry?

Because eating is not only controlled by the stomach.

We eat because of:

• hormones (ghrelin, leptin, insulin)

• brain chemistry (serotonin, dopamine, reward pathways)

• habits and routines

• emotions and stress

• smell, taste, and food availability

• sleep quality and seasonal changes

Appetite is a complex system designed to keep us alive—and sometimes that system is triggered even when the body doesn’t truly need food.

You might also be interested in reading an article on 'What is your relationship with food?'

Key Takeaway

If you want to support healthy appetite regulation, focus on the basics:

• balanced meals (protein + complex carbohydrates + healthy fats)

• enough sleep

• regular meal timing

• stress management

• more whole foods, less ultra-processed foods

• mindful eating habits

Because sometimes the problem isn’t “lack of willpower”—it’s biology.

Learn more here about a balanced nutrition.

Learn more here about how you can improve your sleep.

Learn more here how you can better support your body through stress.

If you want want to improve your diet, but are unsure what to focus on first, what could work with your resources and lifestyle, don't hesitate to reach out to me for personal nutrition counselling. Learn more about my services here: https://www.katrinpeo.com/services.