I have been aware of the hormone Leptin being part of our appetite control mechanism for some time, but having done some more in depth research in to it, Leptin appears to tie together various physiological functions, like weight set point, metabolism regulation and even, in some cases, infertility.
Leptin was only identified in the mid 90s and its functions are still being researched. So, what does Leptin do?
Leptin is a hormone made in our fat cells and communicates directly with the hypothalamus in the brain. The hypothalamus controls, among other things, thyroid function, and therefore metabolism, hunger signals and appetite, including if food is really appealing or not, and energy levels.
The more body fat you have, the more Leptin you produce. It appears we all have an optimal level of Leptin and your brain will up or down regulate depending on how much Leptin you are producing.
When your fat levels increase, your Leptin output increases and your hypothalamus then suppresses appetite, makes food appear less appealing and stimulates metabolism, making you feel more energetic and therefore more inclined to exercise.
As a result of eating less and moving more, you burn up some of your body fat, Leptin levels decrease and your body is back in harmony – ideally. Conversely, if you go on a crash diet, have liposuction, where the fat is sucked out of you, or if you over exercise and under eat, your fat levels drop quickly, your Leptin out put correspondingly reduces and your brain gets the message that famine is afoot (remember, our brains are still functioning as if we are living in caves and surviving on times of feast and famine).
When Leptin levels drop below your bodies ideal level, the hypothalamus goes in to action down regulating thyroid function to slow your metabolism and reduce energy output so you feel tired and less inclined to exercise and up-regulates your hunger signals, making you not only more hungry but food becomes far more appealing. This is why crash diets do not, will not and cannot work long term as will power will never override the brains demand for more food.
It is in this mode that some women will find conceiving very difficult as low Leptin levels give your body the message that there is not enough body fat to sustain a pregnancy.
This brilliant function of homeostasis i.e. maintaining the body’s equilibrium, does not explain why so many people are overweight as this mechanism is designed to maintain optimum fat levels.
When Leptin was first discovered it was thought that giving overweight people Leptin supplements would suppress appetite, increase energy and the problem would be solved. But Leptin supplements work only for people who do not produce any Leptin. This is very rare. Most fat people produce loads of Leptin. The problem is, their Leptin is not able to cross through the blood-brain barrier and get to the receptor sites on the hypothalamus where the message to stop eating is sent i.e. they are Leptin resistant.
Leptin resistance results in the very opposite of a healthy high Leptin response as the brain is not receiving the message so actually thinks Leptin levels are low. Therefore, you are going to be constantly hungry, never satisfied and very disinclined to exercise – now it makes sense, no?
What causes Leptin resistance? – the usual culprits: sugars, especially high fructose corm syrup; high blood triglycerides – closely associated with excess sugar intake and insulin resistance; poor quality fats; lectins in grains (see previous blog); – as lectins bind to Leptin receptors; stress; high toxicity levels and lack of sleep.
How to remedy this….. the usual good guys: omega 3 fatty acids significantly improve Leptin sensitivity; eating good quality meals on a regular basis; good quality, regular, sleep; regular exercise; reduction in sugars.