Leptin and Ghrelin: Why Hunger Isn’t Just About Willpower
If managing your appetite feels harder than it “should” be, you’re not broken and you’re not lacking discipline. Hunger is controlled by powerful biological systems designed to keep you alive, not slim. Two of the most important players in this system are hormones called leptin and ghrelin.
Understanding how these hormones work helps explain why fat loss can feel like a constant battle for some people, and why medications like Ozempic have become part of the conversation.
This article is not about judgment or shortcuts. It’s about understanding how the body actually works.
What is leptin?
Leptin is often described as the body’s “fullness” or “energy storage” hormone. It is made mainly by fat cells and travels to the brain to help signal that you have enough energy stored.
In simple terms:
More body fat usually means more leptin
Leptin should help reduce appetite and support energy balance
The problem: leptin resistance
For many people with overweight or obesity, leptin levels are already high. The issue isn’t a lack of leptin, but that the brain becomes less responsive to it. This is known as leptin resistance.
When leptin resistance is present:
The brain does not receive a strong “I’m full” message
Appetite remains higher than expected
Losing weight becomes harder than simple calorie maths would suggest
This is biology, not a personal failure.
What is ghrelin?
Ghrelin is often called the “hunger hormone”. It is produced mainly in the stomach and rises when you haven’t eaten for a while. It falls after meals.
Ghrelin:
Increases hunger
Encourages food seeking behaviour
Is influenced by sleep, stress, and dieting
This is why poor sleep, long gaps between meals, or aggressive dieting can make hunger feel intense and urgent.
How leptin and ghrelin work together
Think of leptin and ghrelin like opposite sides of a set of scales:
Ghrelin pushes hunger up
Leptin helps turn hunger down
When body weight drops, leptin levels usually fall and hunger signals increase. The body interprets weight loss as a potential threat and tries to restore lost weight. This is one reason why keeping weight off is often harder than losing it in the first place.
Your body is trying to protect you, even if that protection feels unhelpful in the modern world
Why dieting often feels harder over time
As weight is lost:
Hunger hormones often increase
Fullness signals weaken
Energy levels may drop
This makes it easier to regain weight and harder to maintain progress. This response has been well documented in research and helps explain why repeated dieting often leads to cycles of loss and regain.
Again, this is physiology, not lack of effort.
Where medications like Ozempic come in
Ozempic is the brand name for semaglutide, a medication originally developed to treat type 2 diabetes. It belongs to a group of drugs known as GLP-1 receptor agonists. These medications affect the same appetite control systems that leptin and ghrelin are part of.
What does Ozempic actually do?
In straightforward terms, GLP-1 medications:
Reduce appetite in the brain - They help people feel less hungry and less preoccupied with food.
Increase feelings of fullness - Food stays in the stomach slightly longer, especially early in treatment.
Improve blood sugar control - This is particularly helpful for people with insulin resistance or diabetes.
Many people describe this as a reduction in “food noise”. Eating becomes calmer and more manageable, rather than a constant mental struggle.
How effective are these medications?
Large studies show that semaglutide can lead to significant weight loss when combined with lifestyle support. Benefits are generally maintained while the medication is continued.
However, research also shows that when the medication is stopped, much of the lost weight is often regained. This supports the idea that obesity is a long-term condition and that, for some people, ongoing treatment may be required.
How does this relate to leptin and ghrelin?
Ozempic does not replace leptin or block ghrelin directly. Instead, it supports appetite regulation by acting on related brain pathways.
This can help:
Offset weak fullness signals
Reduce hunger during weight loss
Make calorie control feel more achievable
For some people, this support can be life-changing. For others, it may not be necessary.
What role do genetics play?
Body weight is strongly influenced by genetics. This does not mean weight is fixed, but it does mean people start from very different biological positions.
Most people: many small genetic influences
Most weight related genetics affect appetite, food reward, and how strongly the body pushes back against weight loss. Some people are simply wired to feel hungrier or regain weight more easily.
A smaller group: stronger appetite pathways
A small number of people have genetic differences that strongly increase appetite from a young age. These differences affect the same brain systems involved in hunger and fullness.
At present, genetic testing cannot reliably tell us exactly who will benefit most from Ozempic. What genetics does help explain is why weight management is harder for some bodies than others.
Potential benefits of long term use
Research suggests potential benefits may include:
Sustained weight loss while on treatment
Improved blood sugar control
Better blood pressure and cholesterol levels
Reduced risk of heart related events in high risk individuals
Potential risks and considerations
Like all medications, GLP-1 drugs come with risks.
Common considerations include:
Digestive side effects such as nausea or constipation, especially early on
Gallbladder issues, particularly with rapid weight loss
Loss of muscle mass if weight loss is not supported with strength training and adequate protein
Weight regain after stopping, which is common
Concerns around pancreatitis and thyroid cancer are often raised. Current large reviews have not shown strong evidence of increased risk in humans, but ongoing monitoring continues.
These medications should always be used under medical supervision.
The most important takeaway
Whether someone uses medication or not, the foundations of good health remain the same:
Regular resistance training
Enough protein to protect muscle
Adequate sleep
Stress management
A realistic, sustainable approach to eating
Medication is not a shortcut or a failure. For some people, it is simply another tool that helps level the biological playing field.
At Griffin Fit, the goal is never judgment. It’s about understanding the body, respecting individual differences, and using evidence-led strategies to improve health long-term.
If fat loss feels hard, that doesn’t mean you’re doing it wrong. It often means your biology needs support, not criticism.
