Where is it secreted?
Ghrelin is mainly secreted by the stomach, but ghrelin has been identified in other peripheral tissues as well – the gastrointestinal tract, pancreas, ovaries, adrenal cortex.
Ghrelin secretion is dependent on nutritional status – when the stomach is empty.
How it reaches the brain?
There are suggestions of three different pathways by which ghrelin transmits signals to the brain and causes hunger.
– After the release from the stomach into the bloodstream ghrelin can cross the blood-brain barrier and bind to the corresponding receptors in the hypothalamus.
– Ghrelin can reach the brain via the vagus nerve and the terminal nucleus of the medulla.
– Ghrelin is produced locally in the hypothalamus, and directly influences the various centers in the gland.
How does it affect energy balance and food intake?
Ghrelin is a short-term regulator of body weight – when levels are high, we are hungry, and this is happening right before eating.
When you eat, its levels fall.
If your goal is weight loss, it means you need lower levels of ghrelin. If you want to increase your weight, ghrelin must be sufficient to have the appetite to want to eat more.
Can we influence the leptin and ghrelin levels through diet?
Food intake has significant effects on circulating levels of leptin and ghrelin. Eating increases leptin production in healthy people. On the other hand fasting causes almost double increase in plasma ghrelin levels before each meal.
Not only the size and frequency of the meals have an effect on circulating levels of leptin and ghrelin, but also the meal composition plays a role.
|Type of Meal||Leptin||Grrelin|
|High fat||24-hour circulating leptin levels
decrease, which also applies to the high carb meal.
|High Carb||Decreases by greater rate compared to a high fat meal
|Low fat / high carb diet||Increases (at a higher rate compared to high fat/ low carbohydrate diet)||No increase|
|High Fat / Low carb diet||Increases|
|High protein||No effect||conflicting results|
Both leptin and ghrelin play major roles in controlling the energy balance system. Leptin is involved in long-term regulation and ghrelin in the short term regulation. In contrast to leptin, ghrelin did not seem to be critical for normal appetite and growth.
Although the systems of these two hormones act alone, their performance (while maintaining energy homeostasis) includes several overlapping paths.
There are studies that suggest that the hormonal mechanisms controlling appetite, can be different for men and women. This difference comes from the difference in hormonal setup.
– Ghrelin is affected by the release of growth hormone, but it is different in men and women. Leptin influences the reproductive capacity of women, which is related to levels of body fat. Women are more sensitive to leptin, than men.
There are a lot of questions, and some of them have not yet been answered. We need more research on how hormones interact on various factors, because they correspond with each other through a complex system.
On thing is certain though – short and intense diets do not lead to long-term success.
Therefore, when you intentionally want to change body homeostasis, do it slowly in order not to get the yo-yo effect.
What else can we do except pay attention to our diet to maintain normal levels of leptin and ghrelin?
It is believed that fish oil (omega-3) and regular sleep have a role in the improvement of leptin and ghrelin levels.
– Omega-3 fatty acids are associated with a decrease in hunger.
– Lack of sleep leads to higher levels of ghrelin (we are hungry) and lower leptin levels (we are not full), and furthermore it disturbs the glucose metabolism and insulin.
– Do not forget regular exercise, tailored to your individual goals and abilities.