Leptin Signals Our Brains That We’re Hungry

What is leptin?

It's a protein that's made in adipose tissue. Many scientists believe it plays a key role in the regulation of metabolism and hunger. Like insulin, it seems to be a key fat tissue regulator. Evidence shows that the amount of the hormone in the body depends sensitively on the amount of adipose tissue.

When was the hormone discovered, and what kinds of research are underway?

In the 1950s, researchers experimenting on mice discovered preliminary evidence for the existence of the hormone. In 1994, molecules of the compound were finally isolated and studied in depth. Today, research on the compound abounds, often focusing on its potential for controlling obesity in populations.

Could this research hold the key to ending the obesity epidemic?

Since the hormone appears to act on the hypothalamus to regulate our drives (in particular, our appetites), many researchers believe that studying the compound may give us clues about how to change neurological signaling pathways to manipulate behavior. In other words, we might theoretically be able to change our neurochemistry to reduce our drive to consume food.

This may be a fruitful line of research for many reasons. However, if it turns out that the alternative hypothesis about why most people gain weight proves true -- that people fatten because of physiological factors rather than psychological ones, and that therefore leptin changes are downstream effects -- perhaps the field’s research directions will need to be modified.

How does the hormone act on the hypothalamus?

Here is what appears to be the theory: The hypothalamus is the brain's center for controlling appetite; leptin biochemically tells the brain that the body has been satiated. In obese individuals, who have higher than average concentrations of the hormone, this kind of "satiety" signal gets de-sensitized, however. In other words, much like how Type II diabetics suffer cumulative de-sensitization to insulin over time due to insulin “floods” (often brought on by eating carbohydrates) and thus require more insulin to keep blood sugar levels down; obese individuals who flood their brains with leptin repeatedly tend to need to eat more to feel satiated.

Return from Leptin to Glossary

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