Leptin is a hormone produced by body fat that tells your brain (hypothalamus) that you are full. Here's how it works. You eat, leptin is released by your fat tissue, leptin tells the hypothalmus you are full, you lose your urge to eat and then you stop eating. It works well in most of us but scientists have revealed a phenomenon known as leptin resistance. This means that even though the hormone is released by your fat, your brain does not respond to it. The result is that you never really know that you are full so you keep eating. Here are a few things that can cause leptin resistance.1. Inflammation: Poor diet, lack of sleep, food allergies, obesity itself and a host of other variables can promote inflammation. This can shut down the ability of the hypothalamus to respond to leptin. In other words, if you have inflammation going on, then you may not have adequate appetite regulation.
2. Insulin resistance: There is a strong relationship between leptin resistance and insulin resistance. These 2 seem to go together like peas & carrot, peanut butter & jelly etc. Insulin resistance in and of itself is incredibly nasty. But some experts think that leptin levels even set you up for type 2 diabetes. Incredibly, some people who aren't even overweight have leptin resistance!
Journal of American College Health 2006 Nov-Dec;55(3):175-80.
3. Stress: It appears that hyperactivity of the hypothalamic-pituitary-adrenal axis (HPA axis) can lead to obesity. And it appears that the HPA axis is regulated by leptin. While the links are still being drawn, it seems likely that poor leptin regulation may interfere with the HPA axis... subsequently leading to weight gain.
Obesity 2009 Mar 19.
International Review of Cytology 2007;263: 63-102
4. High Triglycerides: When your triglycerides are elevated, leptin has a difficult time reaching the brain because it can't cross something known as the blood brain barrier. Often, triglycerides are elevated in overweight folks. Unfortunately, this means that these same folks are not going to receive the "stop eating" signal. It doesn't seem fair, does it?
Current Pharmaceutical Design 2008; 14 (16): 1606-14.
5. Homocysteine: This is a marker that has been used to predict cardiovascular risk as well as cognitive decline. When you get your routine blood tests, ask your doctor to check your homocysteine levels. Elevations in homocysteine cause leptin resistance.
Molecular Pharmacology 2008; Dec 74(6): 1610-9.
6. MSG: Monosodium glutamate, a common flavoring in processed foods can actually promote leptin resistance. Now I know that some of you are thinking. "In what dose? Is a little bit ok? Just because it happens to rats doesn't mean it happens to humans right?" Let's not make excuses. Even if we can't say with 100% confidence that this happens, the science tells us nothing is good about MSG. At best, it's neutral. At worst, it alters the activity of your brain so that you don't know when you're hungry or full.
Obesity 2008 Aug; 16(8): 1875-80
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