Ghrelin and Leptin: Resetting Your Hunger Hormones Through Smarter Training

Ghrelin and leptin are your body’s key hunger hormones. Leptin helps your body feel safe and nourished, while ghrelin sounds the alarm when energy is low. However, you might be surprised to learn that they are involved in so much more, and imbalances can lead to irregular cycles, weight loss resistance, fatigue, or relentless cravings. 

Their activity is tightly regulated by circadian rhythms, body fat levels, stress, sleep, and especially exercise. Let’s break down what leptin and ghrelin do, how dysregulated hunger hormones manifest, and what exercise patterns support or sabotage their important balance.

Ghrelin: The Hunger Signal

Ghrelin is known as our hunger hormone. It’s the body’s way of signaling energy scarcity, encouraging you to eat and conserve fuel by slowing down fat metabolism. Ghrelin is produced in the stomach and rises before meals, during times of stress, and sleep deprivation. It also interacts with a variety of other hormones. For example elevated ghrelin triggers an increase in cortisol, our main stress hormone. 

Ghrelin can be chronically elevated from extended periods of high stress (elevated cortisol), fasting, and sleep deprivation. Chronically high ghrelin suppresses thyrotropin-releasing hormone (TRH). TRH is produced in the hypothalamus of the brain and triggers the release of thyroid-stimulating hormone (TSH). 

When TRH is suppressed, this results in reduced thyroid gland activity and thyroid hormone production. Low thyroid activity influences nearly all body systems, from reproductive hormones to heart health and metabolism. 

Taming elevated ghrelin levels can help decrease cravings, regulate hunger levels, and support fat metabolism. Ghrelin is best managed through eating satiating meals that are rich in protein and healthy fats, stress reduction practices and supporting healthy stress responses, and doing your best to improve sleep quality.

Leptin: The Fullness Messenger

Leptin is ghrelin’s counterpart, and is made by fat cells. We call it the “fuel gauge” hormone, as it signals to your brain that energy stores are sufficient. Leptin not only curbs appetite, but it also plays a central role in regulating your metabolism, thyroid function, reproductive hormones, and even mitochondrial function.

Leptin is the ultimate stimulator of the brain to ovary connection. It influences the master reproductive hormone regulator, gonadotropin releasing hormone (GnRH), which signals follicle stimulating hormone (FSH) and luteinizing hormone (LH) to be produced in the brain. FSH and LH go on to stimulate the ovaries to produce progesterone and estrogen. And to believe it all started with leptin, a key hormone for fertility!

Leptin levels often drop in those who are underfueling or consuming a low carbohydrate diet. This is a major contributor to the development of hypothalamic amenorrhea, a condition in which the brain stops signaling for ovulation by downregulating FSH, LH, progesterone, and estrogen due to low energy availability.

Taking thyroid activity into account, leptin increases TRH, which we know is critical for triggering the cascade of thyroid activity and thyroid hormone production. Therefore, low leptin levels inhibit optimal thyroid function, which goes on to shape our metabolism, heart health, nervous system, and so much more. 

The amazing activity of leptin doesn’t stop there, it also helps stimulate the production of new mitochondria in muscle cells. This is vital for energy production, athletic performance, maintaining hormonal balance, and supporting long-term health and wellbeing. All of this being said, it is possible for leptin to be too high and for the body to stop responding to leptin activity – this is called leptin resistance.

Signs of Hunger Hormone Imbalances

When ghrelin and leptin are out of sync, your body sends signals that something’s off, whether through constant cravings, low energy, or hormone disruption. While imbalance ghrelin can contribute to these issues, leptin in particular plays a central role in energy balance, fertility, metabolism, and inflammation. Both low leptin and leptin resistance can contribute to very different, but equally frustrating, symptoms. 

Signs of Low Leptin

• Constantly hungry or not feeling full after meals
• Short menstrual cycles, missed periods, or no periods (amenorrhea)
• Fertility challenges and low libido
• Cold intolerance and fatigue
• Reduced bone density
• Insulin resistance (note: both high and low leptin levels can lead to insulin resistance)

Signs of Leptin Resistance

• Constantly hungry (while leptin is high, the brain doesn’t respond due to a lack of leptin receptor sensitivity, therefore appetite stays high)
• PCOS or high testosterone
• Weight gain or difficulty losing weight
• Intense cravings for high-carb foods (and a history of high fructose intake, from high fructose corn syrup or fruit juices)
• Chronic inflammation and blood sugar imbalances
• Low energy levels and frequent illness

How Exercise and Nutrition Influence Ghrelin and Leptin

The way you train and fuel your training has a direct impact on your hunger hormones. While strategic exercise can help optimize leptin and ghrelin, certain approaches can throw them off balance, especially in women.

Supportive Strategies for Hormone Balance

• Prioritize resistance training: Resistance Training is one of the best tools for improving leptin sensitivity and insulin signaling, while also helping to stabilize ghrelin over time. It supports muscle growth and metabolic health, both of which positively influence hormone balance.
• Fuel workouts well: Ensure you are well-fueled to prevent the energy dips that lead to ghrelin spikes and suppressed leptin levels. Consuming enough energy, especially from carbohydrates, is critical for maintaining healthy leptin levels. This is also key for mitigating the cortisol spike that can result from exercise, which is a short-term stress on the body.
• Increase energy for low leptin: If you’re dealing with low leptin levels, work to slowly increase your total energy intake. Focus on consistent meal timing to support your circadian rhythms, and emphasize fiber-rich carbs to send those safety signals to your brain.
• Focus on blood sugar balance: For those with leptin resistance, the main focus is on improving insulin sensitivity and reducing inflammation. This includes balancing blood sugar, limiting excess fructose intake, and addressing any chronic stress.

What to Watch Out For

• Fasted HIIT or endurance training: Especially if you are already in a low-energy state or calorie deficit (common for weight loss), fasted training can increase ghrelin and suppress leptin. This can leave you feeling ravenous all day and hormonally depleted. Because women naturally have higher baseline leptin levels than men, they may experience sharper drops in leptin when fasting. This drop likely contributes to menstrual cycle disruption that often occurs in women of reproductive age while fasting.
• Avoid overtraining and under-recovery: This cannot be emphasized enough to ensure hormones are supported! If you are over-exercising and not allowing yourself adequate recovery time, this propels chronic leptin and ghrelin disturbances. This drives increased cravings, low energy, thyroid and metabolic dysfunction. It could even be a reason you are not seeing fitness progress despite putting in more work.

Train Smarter

Your hunger hormones are not just about appetite – they’re key players in your reproductive function, energy levels, metabolism, and long-term health. Fueling your body well, taking adequate rest, and training with intention are non-negotiables for keeping ghrelin and leptin in balance.

If you’re ready to take a hormone-friendly approach to movement, our Strength in Hormones workout program is for you! In this program, we’ve blended the best methods of strength training with low intensity cardiovascular exercise to maximize fitness in a way that supports hormone health and wellbeing. Join us today!

Written by Romana Brennan, MS, RDN