There's no doubt that certain foods have health benefits, including improving heart health, reducing inflammation and supporting your immune system. But foods aren't a cure-all — particularly when they don't contain the "thing" you're looking for. And in this case, that "thing" is the hormone leptin.
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So, what is leptin? It's a hormone released by our body's fat cells (adipose tissue) and it inhibits appetite, explains registered dietitian Natalie Rizzo, RD of Greenletes. Leptin is directly connected to body fat and obesity, according to the Hormone Health Network.
Ultimately, leptin is designed to help maintain your body weight; it monitors how much fat our bodies have, explains Timothy J. Kieffer, PhD, professor of molecular and cellular medicine at the University of British Columbia.
When your body is functioning correctly, excess fat will produce leptin and signal to the brain that you're no longer hungry. But people with overweight or obesity have high leptin levels, which results in a lack of sensitivity to leptin, which is known as leptin resistance, per the Hormone Health Network.
"Leptin probably evolved to protect us from becoming too thin," Kieffer says. "Lose weight and our body will fight against it, through leptin. The system is more geared to defend against weight loss than weight gain."
Leptin Is Not Found in Food
Even though leptin is associated with appetite, you're not going to find it any food, Rizzo says. That's because it's a hormone. The same goes for the hormone ghrelin, which increases appetite.
"But people might be Googling foods high in leptin because its job is to make you feel less hungry," she says, pointing out that for some 20 years researchers have been trying (and failing) to figure out how to manipulate leptin to help people lose weight.
Why Food Can't Increase Your Leptin Levels
Yes, eating foods high in certain nutrients — vitamin D, protein, folate, to name just a very few — increases your body's levels of those nutrients.
But because leptin is a hormone, not a nutrient, there is no food you can eat to increase leptin levels, Rizzo explains.
Kieffer points out that technically, any food that increases body fat will increase leptin levels, but he says that might only be a goal if someone has severe underweight.
Can Lowering Your Triglycerides Help Increase Leptin?
Triglycerides are the most common type of fat in your body, according to the U.S. National Library of Medicine. They're found in fatty foods, particularly saturated fats like butter.
But triglycerides also come from excess calories that your body doesn't need right away. Those excess calories are converted into triglycerides and then stored in fat cells until they're needed for energy.
While the research is tenuous, some experts think high levels of saturated fat could lead to leptin resistance. An August 2009 paper published in the Journal of Clinical Investigation found that a diet high in saturated fat leads to leptin resistance in mice. While this study looked at animals, the researchers think the findings are likely to apply to humans, as well.
But it's unlikely, Rizzo says, that decreasing your triglycerides would increase your body's leptin levels. The research just isn't there. Kieffer agrees: "That doesn't make sense to me."
Getting enough sleep, however, is crucial to maintaining healthy hormone levels, including those for leptin and ghrelin. A lack of sleep has been associated with increased ghrelin levels and decreased leptin levels, according to a small December 2004 study in the Annals of Internal Medicine.
- Hormone Health Network: "What is Leptin?"
- U.S. National Library of Medicine: "Triglycerides"
- Journal of Clinical Investigation: "Palmitic Acid Mediates Hypothalamic Insulin Resistance By Altering PKC-θ Subcellular Localization in Rodents"
- Annals of Internal Medicine: "Brief Communication: Sleep Curtailment in Healthy Young Men is Associated with Decreased Leptin Levels, Elevated Ghrelin Levels, and Increased Hunger and Appetite"