Leptin, Your Brain and Bodyweight

Your Brain and Your Bodyweight

When people think of losing weight, most people won’t think of their brains.  They think of crunches to “tighten their core” or “chicken breasts and salad” as though those are the only foods acceptable to eat.  Don’t get me wrong, there’s nothing wrong with crunches, chicken or salad, but there’s a larger component missing when you don’t take into account why so many people fail at diets.

Think about it, if someone is overweight then they have “extra fuel,” stored as fat, and should be able to go on a diet and lose weight rather easily because they have a fuel source available to them.  As we all know though, that’s not the case and dieting tends to be quite hard, at least over the long haul.  The question becomes, why is it difficult?  The answer to this question started to come into light in 1994 when researchers found a hormone released by fat cells called Leptin. 

Leptin: Master of Your Metabolism

The initial research on leptin was done on rats and showed that rats who didn’t produce leptin were grossly overweight.  In contrast, those rats with normal leptin levels were of normal body weight.

No Leptin vs Leptin mice2 300x203 Leptin, Your Brain and Bodyweight

Having No Leptin vs Having Leptin

When leptin was first discovered, researchers thought they had struck gold.  Finally, the hormone that needs to be controlled for people to become skinny.  At least, that was the idea.  If rats without leptin were grossly overweight, then just giving them leptin would make them skinny.  And guess what?  It did.  Giving the rats who didn’t make leptin some synthetic leptin made them skinny.  This was exciting news.

In other words, it was theorized that those with low leptin levels would be overweight and those with high leptin levels would be naturally skinny.  As this research was still young, it was still naïve.  As the research moved onto humans, it was discovered that only a very small percentage of people didn’t make leptin, whereas most overweight and obese individuals actually had high leptin levels.

It wasn’t that obese people didn’t make leptn, like those rats, but instead the signals leptin was sending, weren’t being heard.

You see, leptin works on your hypothalamus (part of your brain) and its main job is to keep you alive by keeping your body weight within a certain range.  It’s similar to how a thermostat works in that, despite fluctuations in the outside temperate (fluctuations in how much you eat), leptin will do things that try to keep your weight within that certain body weight.

If you over-eat, then lots of leptin is released and sends signals to:

A – Decrease your appetite.  You feel full all the time and fights the effects of another hormone called ghrelin, which stimulates hunger.

B – It tells your body to release more TSH (thyroid stimulating hormone) and speeds up your metabolism a little bit.

C – This in turn, amps up heat production (more energy being expended) and most people naturally increase their fidgeting (can add up to a couple of hundred extra calories burned per day).

Leptiin production 213x300 Leptin, Your Brain and Bodyweight

On the other hand, if you go on a crash diet, then leptin signals drop considerably and tells your body to:  

A – Increase appetite.  Without opposing ghrelin, your appetite is greatly increased.  High levels of ghrelin are responsible for increases in sugar and sweet cravings.

B – Decreases TSH release.  In other words, your body’s production of your thyroid hormone production drops.  This causes your metabolism to decrease dramatically.  In fact, research has shown that just a week of crash dieting can decrease your basal metabolic rate by 40% (that’s close to a 800 calorie deficit per day with just a week of crazy dieting).   This is why most “weight loss cleanses” suck (period).

C – You end up feeling tired, cold and overall sluggish, causing you to not only move less, but decreases your motivation to exercise.

Leptin, Your Brain and Headphones

Overall, leptin correlates with how much fat you have.  So if you have a lot of fat, you will have a lot of leptin and if you are skinny, you don’t have as much.  The best way to visualize how leptin works in the human body is by thinking about having a conversation with another person.

When your brain hears the signals that leptin is sending it, this system works pretty well to keep you within a certain body weight.  You can think of this as someone talking to you in a normal day to day conversation.  If your hearing isn’t impaired, you understand the person and as such, you have a conversation that goes back and forth.  This is what happens with your body, leptin and brain.  If you get sick and don’t eat for 4 days, leptin levels drop and you might lose some weight.  Once you start to feel better, with the low leptin levels, your appetite is increased and you start to eat more than you normally would and usually gain the weight back.  This keeps you healthy over the long-term and helps to keep you alive.

The problem is what happens when those signals aren’t being heard.  This is like putting on your iPod headphones and turning the volume all the way up.  A person can be sitting right next to you, talking to you as loud as they can, but you don’t hear them.  Here the signals aren’t being heard and instead of a conversation, you are instead having someone basically scream at you and you are not responding.  This is what happens to your brain when you’ve become overweight or obese for a long time.  Leptin is screaming at your brain that you shouldn’t eat any more, that you’re full and that you should increase your metabolic rate, but those messages aren’t being heard.  Your brain has those headphones on and despite your body screaming at it, it’s not hearing the messages.

So the simplistic equation into body weight and body weight set point looks like this:
Lean individuals = Small amount of leptin + Sensitive leptin signals

Obese individuals = High amount of leptin + Unheard leptin signals

The question becomes , “How do you ‘take those headphones off’ so your brain can hear those signals again?”

Get Your Body to “Hear” Leptin Again

To answer this question, you have to look at people who have low levels of leptin and are still very sensitive to its effects.  For these people, instead of headphones on, they have super hearing aids in.  For them, leptin doesn’t have to send strong signals to be heard and as such, remain relatively lean, effortlessly.

Here’s the thing, being lean is the way that the human body is “supposed” to be.  Sure, there are different body types and different tolerances to carbs and fat, but overall, most people should be relatively lean.

With that said, there is research highlighting the differences between those who naturally have low levels of leptin (the Kitavans) versus those who have higher levels of leptin (the Swedes).  The Kitavans are a hunter-gatherer society and in the picture below they are contrasted against healthy Swedes.

Male Leptin Levels Sweden vs Kitava1 Leptin, Your Brain and Bodyweight

As you can see, the dark dots representing the Kitavans had much lower leptin levels and hence, lower overall weight.  Beyond a few outliers, all of the Kitavan men had leptin levels under 4.5 ng/mL.  The Swedes, on the other hand, had a much higher concentration of leptin and hence, higher body weights.

So what are some things that the Kitavans did differently to keep their Leptin levels low?  Next week’s post will highlight 7 actionable steps that you can control to give yourself the best odds of having those leptin signals be heard again.

For now though, I will tell you four important distinctions between the two groups of people in the research, of which you may not have had control over, especially when you were younger:

A – The Kitavans never had a “sweet tooth” that was indulged upon when they were younger.  When I was young, I had a huge sweet tooth and that can dramatically mess up one’s ability to hear leptin’s signals for a very long time.  Although you can take control over a sweet tooth, it makes it much harder to keep your body fat levels low, especially as you get older.  Next week, I will discuss ways to move past a sweet tooth.  Although it’s not easy, it’s doable.

B – They were never overweight.  Childhood obesity is a huge problem in this country.  Here’s the thing, epigenetics points to a direct correlation between parent’s body weight (and the amount of food in the womb) and the incidence of obesity later in life.  In other words, what your mother ate can have a large influence on your bodyweight later in life.

Research, not yet published, has shown that the only way to fight this trend is through lots of physical activity when you’re young.  In other words, let kids play and ensure that they can do so at school.  People will gain most fat cells, which tend to stay with them for life…and is correlated with leptin levels, from the third trimester to about 18 months and around puberty.  If you can stave off an undue amount of fat gain during puberty and increase activity when kids are younger, you give them an upper hand at staying lean for life.

C – The Kitavans didn’t have C-sections and were breast fed.  As more and more research continues to point out, the bacteria that we are first inoculated with (from a natural birth and being breast fed) can have huge implications for inflammatory responses, overall health and obesity throughout life.  If you have the option to have a natural birth and breast feed your child, do so.

D – They were never fed “food-like substances.”  They never had their signals interfered with by margarine, vegetable oils, high fructose syrup, fat-free milk products, refined grains and refined sugar.

Until Next Week

Last week’s post on genetic differences between weight loss with exercise, weight gain with over-eating and one’s body weight set point led to this week’s post highlighting the role of leptin in one’s body weight.  Next week, I will finally get to the 7 Factors you can control to lower leptin levels, maintain weight loss and do so, while staying healthy.  If you have any questions before then, please feel free to let me know.

Here’s the link for part 1 of The 7 Principles of Permanent Fat Loss.

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