Hunger Hormones and the Unknown in the Science of EatingheadingContent
The two main hormones to regulate hunger are leptin, which works to stop hunger, and ghrelin, an activator in creating an appetite for food. Leptin works to stop hunger therefore assists in weight loss. Ghrelin is the primary feeding hormone to activate hunger. One would think that an overweight patient would have high levels of ghrelin and low levels of leptin but studies are finding that the exact opposite is true. What we believe now is that although there is a high level of leptin circulating, the body is resistant to the hormone.
Leptin originates from fatty tissue in response to energy stores. Other factors that influence its release are: (sugar intake, sleep cycles, gender, age and amount of exercise on a regular basis). Once leptin levels rise, hunger is perceived and metabolism is increased. Currently, there are no available medications that directly alter leptin levels.
What leads to higher than expected leptin levels in overweight individuals?
Scientists believe that long term patterns of over eating (eating beyond feeling full) may lead to development of resistance to this hormone. Meaning, you need higher concentrations in order to receive the “I am full” signal.
How do diets affect these hormones?
Binge eating leads to increased leptin and may lead to eventual leptin resistance- making it harder to feel full. Food composition and meal size also affect the levels of hormones released. A larger, more carbohydrate dense or low fat meal, leads to a higher leptin rise than a small low carbohydrate or high fat meal.
Putting all these facts together we can see that in order to optimize weight loss one should eat small frequent meals, composed of low carb and higher (healthy) fats. Exercise decreases body fat stored and should, in theory, decrease the cells responsible for the hunger signal.
Ghrelin, on the other hand, seems to be mainly released from the stomach in response to nutrition status. As levels rise, hunger levels rise. Fasting therefore causes levels to rise. There are no commercially available medications to altar ghrelin levels. There are genetic conditions that have higher than normal levels of ghrelin, which can lead to increased appetite and weight.
Information was taken from a review article: The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. By MD Klok, S Jakobsdottir and ML Drent. Published in 2006 in The International Association for the Study of Obesity.