Leptin: The Golden Key to Appetite

One of the most interesting things I've read about when researching nutrition is the hormone leptin, so named from the Greek word leptos, meaning "thin." The reason why I find leptin interesting is because frequently when people think of going on a diet, they think they need to starve themselves (relatively speaking). "I just need to eat less and exercise more" is a common way to think about a new year's resolution to lose weight. The problem with this strategy is that you're hungry and the plan is unsustainable for a specific scientific reason: leptin. Control your leptin and you control your appetite. Once you control your appetite, it is MUCH easier to be selective about what food you choose to eat. So, today, let's learn about leptin because LEPTIN IS AWESOME.

Leptin is a protein that is made in your fat cells and is transported to your brain through your bloodstream. Leptin tells your hypothalamus (a specific area of the brain) that you have enough energy. Leptin is kind of like your food accountant, it tells the brain you've eaten enough food and stored enough energy to engage in activity. Just like a good accountant, leptin says, "Your cash/energy flow is positive and you've got enough to cover all your essential expenses, so feel free to go spend some money/energy on other things." Most important of all: You are not in starvation mode when leptin is talking to your hypothalamus.

What is starvation mode you ask? Let's say you're on one of those extreme "juice cleanse" diets. Leptin is not being sent to your brain and, as a result, your brain senses starvation and goes into survival mode. Your brain and body's primary goal right now is to get you fed. So the brain sends a signal to your vagus nerve (the longest cranial nerve in the body that stretches all the way to your abdomen) and that causes the feeling of hunger. Your brain also sends a signal to your thyroid that slows your metabolic rate. In starvation mode, your body is doing everything it can to extend the energy stores you have until you feed it again. So here you are, trying to drop a few pounds, and your body is working in overdrive to hold onto fat until you give it some food. Seems a bit inefficient, no?

Here's another way your body is working against you and your juice cleanse: Once leptin gets to the hypothalamus it sets off these "leptin-responsive" neurons in your brain. These neurons feed directly into the dopamine system, which controls the brain's reward and pleasure center. The lower your dopamine level, the more rewarding food becomes. The higher your dopamine level, the less rewarding food becomes. THIS IS NOT ABOUT WILLPOWER PEOPLE. You are biologically programmed to properly feed your body. So if you can't starve yourself to lose weight, what can you do? Eat the right foods. Eat the foods that keep your leptin and dopamine levels high. I promise to help us all figure out what those are. I just can't do it in the space of this post. The good news is that the ones I know about taste really, really good -- and are SO much better than endless glasses of brownish green juice!

Now, there's a wrench in this explanation that I'm sure you guys are bound to catch. Don't obese people have lots of leptin if it's generated by fat cells? Yes, an obese person does have high leptin levels, unfortunately, there is something blocking the leptin from getting to the hypothalamus. There are particular foods that make this happen. I'll get into this in more detail later as well. But here's something to get you thinking: Ever notice how certain foods never make you full? Like that time you sat down with a bag of potato chips and ate the whole thing? You were like, holy crap, where did that bag of potato chips just go?  Those potato chips were not generating any leptin, but they did give your body some carbohydrates which it is going to store until you give it what it really wants.

The key to controlling leptin is knowing which foods allow it to function normally and which foods block it from signaling your brain. It probably doesn't come as a surprise to you that many of the most well-known "bad" foods are not conducive to leptin functionality (e.g., chips, soda, cupcakes), but there are also a lot of other foods that might surprise you. What also may surprise you is the food that is conducive to leptin functionality: fat. Heart advocates, please indulge me, we have been very misled about fat. When you eat the right fat, it's not going to clog your arteries, but we'll get into the different types of fat and what your body does with them in another post.

The main thing to take away about leptin is that the right foods make you full (and happy!) and don't cause you to gain weight. Leptin does all your accounting for you (no calorie counting!) if you eat the right foods. Furthermore, if you are already full, eating a bag of potato chips is not appealing to you. If you eat the right food, you will feel satisfied and your leptin and dopamine levels will be high. If you eat the right food, you will be less hungry and more happy. Sounds like a win-win, right?

Dr. Lustig has a lot to say about leptin, you can read more about this amazing protein here, here, and here.

The Chasm Between Weight and Health

After reading my post yesterday, a friend of mine sent me a message about how she frequently felt judged for her small size (OMG, she must purge all her food, GAH, go eat a cheeseburger!) and found it comparable to how we judge people for being a larger size. She also kindly shared with me that she lost her dad to heart disease; even though he was very slender, he was certainly not healthy. I really appreciate her reaching out, and it made me realize that I needed to discuss this in further detail before moving forward with other posts.

My friend's story about her dad also reminded me of an article I read ages ago in Runner's World about an ultramarathoner who suffered a heart attack in his early 30s. Genetics? Perhaps. A diet extremely high in simple carbohydrates that he explained in great deal? In my humble opinion, this is the more likely culprit. I plan to do a post on the mounting evidence of sugar causing heart disease, but for now, I will simply state that is my opinion. Don't believe it until you read the evidence for yourself.

Too often we attribute weight to health when it's really just one of many factors and certainly, in my opinion, void of the most important factor: what do you actually eat. So I feel the need to set the record straight: size does not determine how healthy you are. I chose to start this discussion of health and nutrition based off of weight gain because I think it is something most people can relate to. My grander purpose is to get us thinking about health instead of weight. There are lots of overweight people who are not binge eaters, just like there are lots of skinny people who are not binge eaters. The morbidly obese and the emaciated actually have a lot more in common than meets the eye: their bodies are starved of the nutrients they actually need. You can be a medically defined "ideal weight" and be much less healthy than an overweight person. For example, you could have lung cancer, or any other number of diseases that have nothing to do with being overweight. This is how some parts of our medical lexicon play into nutritional misinformation. In fact, recent evidence shows a correlation between being overweight and having a longer lifespan. I would purport that, it's not the excess weight that's helping the overweight live longer, but one macronutrient in particular that is essential to the body (particularly the brain) that also helps absorb micronutrients. The overweight may be eating this macronutrient in addition to the food that causes them to be overweight. A slender person could also be eating this macronutrient without gaining any excess weight. (I will discuss this lovely macronutrient, my favorite of them all, in great detail, in another post.)

So please, pretty please with a cherry on top, stop judging other people based on their outward appearance/weight, and, more importantly, stop judging yourself based on your outward appearance and/or weight. The reason I wrote the "ultimate fat trap" post relatively early on in this discussion is because I want us to really see how little evidence our judgments are based on. And, furthermore, how little evidence our nutritional guidance is based on. It's enough to make anyone throw up their hands and say "screw it, I'll eat what I want."

Learn what foods are good for you and indulge in your favorites; may you find pleasure in food and find pleasure in health. Feed your body, feed your mind, and feed your soul with positive things. I hope my blog can help guide you a little bit in finding what things are actually good for you, as well as delicious and satisfying, and to stop the judging, depriving, binging, purging, or any other disadvantageous activity. I hope that we can do it together actually. I am learning and growing right beside you, and I think I can help us both ask the right questions. The hardest part of this equation is figuring out what foods are actually good for you, and I think we may actually be able to figure this out. Please, join me!