For a lot of people, the word 'hormone' brings back memories of sex ed classes in school, where the standard response was to blush, tune out, or both. What many people don't know is that our bodies produce a huge array of different hormones – a hormone is a chemical which carries a message from one part of the body to another - and these have a role to play in almost everything our body does, so wipe that smirk off your face and pay attention!
There are literally hundreds of different hormones involved in the processes that surround eating. Most people will have heard of insulin, which is a hormone responsible for controlling blood sugar levels, but fewer will have heard of Leptin and Ghrelin, the hormones that control hunger and satiety.
Leptin and Ghrelin are known as the "Hunger Hormones" because they play a huge role in controlling our appetites. It is thought that being able to exert control over these hormones could be the key to weight loss. Let's take a look.
What is Leptin?
Leptin is a protein hormone that was only fully characterised earlier this century. It is produced by our fat cells, and has receptors in the brain. Early researchers noted that leptin deficiency led to insatiable hunger and obesity, and we now know the complex mechanisms through which leptin tells the brain to switch off the appetite and burn fat for energy (1).
Research has shown that obesity is linked to Leptin resistance. When high levels of leptin are sustained over a long period, the leptin receptors shut off, just like insulin receptors become resistant to constant high insulin levels, causing type 2 diabetes. This offers an explanation for the fact that the people with high levels of body fat produce more leptin, yet high levels of this appetite suppressing hormone fail to reduce bodyweight (2).
On the other hand, leptin can make weight loss difficult. Leptin production is proportionate to fat mass and studies have shown that levels decrease significantly when someone is losing weight, slowing down the metabolism and increasing the instance of hunger (3). A leptin analogue has recently been approved by a number of regulatory bodies worldwide, including the US FDA, for the treatment of lipodystrophy, which is a rare disease affecting fat metabolism. The company is currently seeking regulatory approval for leptin to be used in the treatment of other metabolic illnesses (4).
What is Ghrelin?
Like Leptin, ghrelin is a protein hormone, and it too was only discovered and fully characterised relatively recently. Ghrelin is secreted by cells in the lining of the stomach and intestines, and targets receptors in the brain, which are located on the same cells as the receptors for leptin (5).
Ghrelin can be thought of as having an opposite effect to Leptin. Ghrelin secretion is tied to the level of stretching in the stomach. When the stomach is empty, ghrelin is secreted, transmitting messages of hunger to the brain. When the stomach is stretched, as is the case after a meal, ghrelin secretion is turned off (3).
Losing and gaining weight also has effects on ghrelin levels. Researchers were surprised to find that ghrelin is secreted at low levels in obese people, and have hypothesised that excess weight increases a person's sensitivity to ghrelin, meaning that less of the hormone is required to invoke feelings of hunger (1). Ghrelin can also make losing weight difficult, as studies have shown it is secreted at higher levels after weight loss, increasing hunger (3).
Leptin and Ghrelin's Roles
Both Ghrelin and Leptin play very important roles in the regulation of weight and energy homeostasis, both short and long term, and there is still a lot of research being done into the effects and interactions that make up this system. One thing that has become clear is that the leptin/ghrelin system actively works to maintain current body weight. Levels of each hormone have been observed to alter when weight is lost, slowing down the metabolism and increasing hunger, in an attempt to return the body to its previous form. While these hormone levels do eventually normalise, this protective mechanism can make weight loss difficult.
One way to counteract these effects speeds up your metabolism and suppresses appetite is by using a fat burner supplement. Fat burners contain ingredients like caffeine to curb hunger, and safe, all natural ingredients like L-carnitine and green tea can increase the rate at which your body burns energy.
The way our body regulates weight and metabolism is a lot more complex than competing levels of two hormones, and the discoveries that have been made have not uncovered a miraculous weight loss solution. The best way to lose weight has not changed. While you can't beat diet and exercise for safe, sustainable weight loss, you can maximise the return for your efforts with the help of a fat burner.
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(2) Myers MG, Cowley MA, Münzberg H (2008). "Mechanisms of leptin action and leptin resistance".Annu. Rev. Physiol. 70 (1): 537–556.
(3) De Vriese C, Perret J, Delporte C. Focus on the short- and long-term effects of ghrelin on energy homeostasis. Nutrition. 2010 Jun;26(6):579-84. Nutrition. 2010 Jun;26(6):579-84.
(4) Chou K, Perry CM. Metreleptin: first global approval. Drugs. 2013 Jun;73(9):989-97.
(5) Klok MD, Jakobsdottir S, Drent ML. The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. Obes Rev. 2007 Jan;8(1):21-34.
(6) Perello M, Scott MM, Sakata I, Lee CE, Chuang JC, Osborne-Lawrence S, Rovinsky SA, Elmquist JK, Zigman JM; Scott; Sakata; Lee; Chuang; Osborne-Lawrence; Rovinsky; Elmquist; Zigman (2012)."Functional implications of limited leptin receptor and ghrelin receptor coexpression in the brain". J. Comp. Neurol. 520 (2): 281–94