Which hormones affect hunger, fullness and body weight?
Hunger and fullness are regulated by several different hormones. Ghrelin, which is mainly produced in the stomach, is often called the body's hunger hormone because levels rise before meals. Hormones such as GLP-1 and PYY are released from the gut after we eat and contribute to increased fullness.
Leptin, which is produced in the body's fat tissue, also plays an important role by signalling to the brain about the body's energy reserves. Insulin affects both blood sugar regulation and the body's energy balance by helping cells take up glucose from the blood.
These hormones, among others, interact with the brain to regulate appetite, fullness and energy expenditure. Factors such as sleep, stress, physical activity and body weight can affect how these systems function, which is one reason why weight loss can look different from person to person.
Ghrelin and leptin: hormones that affect hunger and fullness
Ghrelin and leptin are two hormones that play an important role in the body's regulation of appetite and energy balance. Ghrelin is mainly produced in the stomach and contributes to feelings of hunger, while leptin is produced in fat tissue and signals to the brain that the body's energy reserves are sufficient.
During weight loss, the levels of these hormones change. Ghrelin levels can increase while leptin levels decrease, which can lead to increased hunger and make it more difficult to maintain weight loss over time.
This is a normal biological adaptation and one of the reasons why long-term weight regulation can be challenging. Body weight is influenced not only by eating habits and physical activity, but also by hormonal mechanisms that regulate hunger, fullness and energy expenditure.
GLP-1 and PYY contribute to fullness after meals
GLP-1 and PYY are hormones that are released from the gut when we eat. They contribute to increased fullness, affect appetite and help the body regulate energy intake. GLP-1 also affects how quickly the stomach empties, which can help feelings of fullness last longer after a meal.
In people living with overweight or obesity, the body's regulation of hunger and fullness may be altered, which can make it more difficult to feel full and maintain weight loss over time. Body weight is influenced by a complex interaction between biological, genetic, psychological and environmental factors.
GLP-1-based medicines mimic the effects of the body's own GLP-1 hormone. For many patients, treatment leads to reduced hunger, increased fullness and less focus on food, which can make long-term lifestyle changes easier.
Why can it be difficult to maintain weight loss over time?
When body weight decreases, several biological adaptations occur that can make it more difficult to maintain weight loss. Appetite can increase while the body's energy expenditure may decrease slightly, which means the body needs less energy than before.
Research shows that changes in hormones that regulate hunger and fullness can contribute to increased hunger after weight loss. At the same time, spontaneous everyday movement may decrease in some people, which also affects total energy expenditure.
These biological adaptations are one reason why many people find that it becomes more difficult to continue losing weight or maintain the results over time. Obesity is now considered a chronic disease that often requires long-term interventions, where both lifestyle habits and, for some people, medical treatment can play an important role.
Myth vs fact about hormonal weight regulation
Misunderstandings about the body's biology often lead to unnecessary guilt, but modern obesity research shows that body weight is influenced by a complex interaction between biological, genetic, psychological and environmental factors. Understanding how the body regulates hunger, fullness and energy balance can make it easier to understand why weight loss is often more challenging than many people think.
Myth: Overweight is only about a lack of willpower.
Fact: Obesity is a chronic disease in which biological mechanisms affect hunger, fullness, energy expenditure and body weight. Willpower can play a role, but body weight is also influenced by hormones, genetics, lifestyle habits and environmental factors.
Myth: If you lose weight, it automatically becomes easier to maintain your new weight.
Fact: After weight loss, biological adaptations occur that can increase hunger and reduce the body's energy expenditure. These changes can make it more difficult to maintain weight loss over time and are one reason why long-term support is often important.
Myth: If I'm hungry, I just need better discipline.
Fact: Hunger is controlled by several hormones, including ghrelin, leptin and GLP-1. For people living with overweight or obesity, the body's hunger and fullness signals may be altered, which can make it more difficult to reduce energy intake and maintain weight loss.
Myth: Weight loss medicines are a shortcut.
Fact: Modern weight loss medicines affect biological mechanisms that regulate hunger and fullness. For people living with obesity, they are used as part of medical treatment alongside lifestyle changes and follow-up within healthcare.
How stress, hormones and stages of life can affect weight
Several hormonal systems affect body weight and how the body regulates hunger, fullness and energy balance. Factors such as long-term stress and different hormonal changes can affect the conditions for weight regulation.
During long-term stress, the body's production of stress hormones, including cortisol, increases. Long-term stress can affect appetite, sleep and eating habits. For some people, this can contribute to increased energy intake and increased fat storage around the abdomen, while others may instead lose their appetite. The body's response to stress varies between individuals.
For women, menopause involves falling oestrogen levels, which often leads to changes in body composition. Many women find that fat distribution changes and that a greater proportion of body fat is stored around the abdomen while muscle mass gradually decreases. Regular physical activity and strength training can help preserve muscle mass and support health during this period.
Hormonal conditions such as PCOS and hypothyroidism can also affect body weight and make weight regulation more challenging for some people.
Medical treatment can affect the body's hunger and fullness signals
Obesity is a chronic disease in which biological mechanisms affect hunger, fullness and body weight. For some people, these mechanisms can make it difficult to achieve and maintain weight loss through lifestyle changes alone.
Modern weight loss medicines, such as GLP-1-based treatments and medicines that affect both GLP-1 and GIP receptors, mimic the body's own hormonal signals that regulate appetite and fullness. Many patients experience reduced hunger, feeling full sooner and less focus on food, which can make it easier to reduce energy intake and establish new habits over time.
Medication is used as part of a broader treatment plan where the goal is not only weight loss, but also improved health and a reduced risk of obesity-related diseases. For many people, treatment can help counteract the biological adaptations that often occur during weight loss, such as increased hunger and altered energy balance.
At Yazen, medication is combined with support from doctors and other healthcare professionals. Treatment is tailored to the individual's health, goals and circumstances and also includes support with diet, physical activity, sleep and other lifestyle habits to create sustainable changes over time.
Frequently asked questions about hormones and weight loss (FAQ)
Which hormones can be behind weight gain?
Several hormones affect body weight, including ghrelin, leptin, insulin, cortisol, oestrogen and thyroid hormones. Changes in these systems can affect appetite, energy balance and fat distribution. At the same time, overweight and obesity are rarely caused by a single hormone, but rather by an interaction between several biological and lifestyle-related factors.
Why am I not losing weight despite being in a calorie deficit?
If weight loss stops even though you feel that you are eating less, there may be several explanations. When body weight decreases, biological adaptations occur that can increase hunger and slightly reduce the body's energy expenditure, which can make further weight loss more difficult.
At the same time, factors such as sleep, stress, physical activity, hormonal changes and how well energy intake matches the body's needs can affect the results. It is also common for weight loss to happen more quickly at first and then slow down over time.
A weight plateau therefore does not necessarily mean that you are doing something wrong. Long-term weight regulation is often about gradually adapting the strategy according to the body's biological and lifestyle-related circumstances.
Can stress affect weight?
Yes. Long-term stress can affect appetite, sleep and lifestyle habits. For some people, this can contribute to weight gain or make it more difficult to lose weight.
Can there be hormonal causes behind being overweight?
In some cases, conditions such as hypothyroidism or hormonal conditions such as PCOS can affect body weight. At the same time, overweight and obesity are usually caused by an interaction between several biological, genetic, psychological and environmental factors.
How do GLP-1 medicines affect the hormones that control appetite?
GLP-1-based medicines mimic the effects of the body's own GLP-1 hormone. Many patients experience reduced hunger, increased fullness and less focus on food, which can make long-term weight loss easier.
How does menopause affect women's ability to lose weight?
During menopause, oestrogen levels fall, which often leads to changes in body composition. Many women find that a greater proportion of body fat is stored around the abdomen while muscle mass gradually decreases.
Symptoms such as sleep problems, hot flushes and tiredness can affect energy levels and lifestyle habits.
Regular physical activity, particularly strength training, together with sufficient protein intake, can help preserve muscle mass and support health during and after menopause.
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