Insulin, testosterone, cortisol. Nowadays we hear a lot about such hormones, chemical messengers, which can be compared to the software on a computer, acting to control processes throughout your body, which is the hardware. Leptin is another important hormone. It was discovered in 1994 but it’s only in the last few years that we have begun to understand its intriguingly complex role in the body.
One function of leptin is to control sensations of hunger, more specifically satiety or fullness. Normally, when levels of leptin are high your desire to eat is suppressed. Conversely when leptin levels are low, you’ll feel hungry. The hormone is released into the blood from fat cells called adipocytes, and then travels through the bloodstream to a region of the brain known as the hypothalamus (1) reducing the desire to eat.
Leptin follows a natural rhythm, rising and falling throughout the day, with levels being naturally lower in the morning (2), which is why we often wake up feeling hungry ready to eat breakfast.
The hormone is also released in response to high calorie intake, for example, after a meal, on a short-term basis. But leptin regulates long-term satiety, too. Normally, the higher percentage of fat an individual has in their body, the more leptin production there is.
On this basis you would probably think that overweight individuals with a higher fat percentage would have a reduced appetite, as an increase in leptin in the body should decrease the desire to eat. Alas, this is not the case. In fact, in obese individuals, leptin fails to reduce appetite and mediate weight loss. Why? Well, a problem arises when there is a disruption in the leptin pathway leading to a reduced response to the hormone – known as leptin resistance (3). In short, although leptin is being produced, it has little or no effect on the brain. This can be likened to insulin resistance in type II diabetes, where cells have lost their response to insulin.
What Causes Leptin Resistance?
Leptin resistance occurs even though there are often very high levels of the hormone in the blood. Though the definitive cause of resistance isn’t truly understood, there are two main theories. The first is that leptin in the blood is unable to reach its target in the brain. The second, noted above, is that although it may reach the target in the brain, the brain has lost its normal response to leptin. Most researchers favor the latter theory. Note, that researchers have found a close relationship in the way insulin and leptin work in the body, and many believe that insulin resistance actually causes leptin resistance.
But whatever the mechanism of leptin resistance may be, too much leptin appears to disrupt its normal function, leading to an increased appetite.
What Foods Cause Leptin Resistance?
Foods containing high levels of fructose seem to work against the healthy regulation of leptin (4). Certainly, there is compelling evidence from research in rats demonstrating that a regular high-level fructose intake is a cause of leptin resistance. Foods high in fructose include high-fructose sweetened fizzy drinks and certain fruits such as grapes, mango, pears and, especially, dried fruit.
There might be something else going on, too. Lectins (not to be confused with leptin!) are carbohydrate-binding molecules found in cereals such as wheat, barley and rye. Researchers from the Department of Medicine at Lund University, Sweden have suggested that a diet high in cereals may contribute to leptin resistance due to the high lectin content of the grains consumed (5).
Taking Control of Leptin
So what can you do to take control of your leptin levels? There are a few simple dietary changes that may reduce the risk of leptin resistance. Firstly, eat a protein-rich rather than a carbohydrate-rich breakfast first thing in the morning. Breakfast ideas can include eggs, bacon, turkey or a protein shake.
Another very useful dietary change is to minimize your consumption of simple carbohydrates such as glucose and fructose, throughout the day. Also, try to reduce starches such as white flour, pasta, and potatoes. You can also avoid grains to reduce lectin intake, too.
Additionally, cut out snacking, especially late at night. Eat dinner fairly early in the evening and don’t eat anything else afterwards in order to maintain your natural leptin cycle.
Lastly, keep in mind that sleep is important for the normal regulation of many hormonal processes involved in metabolism, including that associated with leptin production. So be sure to get adequate and regular shut-eye.
- Sahu, Abhiram. “Leptin signaling in the hypothalamus: emphasis on energy homeostasis and leptin resistance.” Frontiers in neuroendocrinology 24.4 (2003): 225-253.
- Radić, Radivoje, et al. “Circadian rhythm of blood leptin level in obese and non-obese people.” Collegium antropologicum 27.2 (2003): 555-561.
- Banks, William A., et al. “Triglycerides induce leptin resistance at the blood-brain barrier.” Diabetes 53.5 (2004): 1253-1260.
- Shapiro, Alexandra, et al. “Fructose-induced leptin resistance exacerbates weight gain in response to subsequent high-fat feeding.” American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 295.5 (2008): R1370-R1375.
- Jönsson, Tommy, et al. “Agrarian diet and diseases of affluence–Do evolutionary novel dietary lectins cause leptin resistance?.” BMC endocrine disorders 5.1 (2005): 10.