It Starts With Food: Discover the Whole30 and Change Your Life in Unexpected Ways (6 page)

Hormones also respond to any external factor that tips the scales out of balance. To go back to our thermostat analogy, opening a window in wintertime will push the temperature in your home off balance. The act of opening a window sends a message (“It’s getting cold in here!”) to your thermostat, which reacts to that stimulus with an internal correction (firing up your furnace). When the temperature reaches the normal range again, your furnace then turns off.

When you eat and digest food, various biochemical components of the food trigger multiple hormonal responses in the body. These hormonal responses control the use, storage, and availability of nutrients—where they go and what happens when they get there. Different nutrients cause different hormonal responses, but
all
of those responses are intended to correct the shift in balance caused by the influx of digested food particles.

While there are a lot of hormonal players, for the sake of simplicity, we’re going to talk about only four in detail:

These four hormones (along with many others) form a complex, elegant—but not indestructible—web of feedback loops that influence all body systems. They all interact with one another’s functions, behaving like a team in the body. These hormones are neither “bad” nor “good” in the right amounts. Things get ugly, however, when you’ve got too much or not enough of any given hormone.

Let’s start with both insulin and leptin, as it’s hard to separate these two.

Summary: An anabolic (“building, storing”) hormone secreted by the beta cells of the pancreas in response to ingestion of energy, most notably from carbohydrate. Insulin facilitates the moving of macronutrients (protein, fat, and carbohydrate) from the bloodstream into cells for immediate or future use, and coordinates the metabolic shift from predominantly burning one fuel source (carbohydrate) to the other (fat). Chronically elevated insulin levels are correlated with leptin resistance and indirectly related to elevated cortisol levels.

Insulin is about as close to a “master hormone” as you can get. It acts on virtually all cells in the body and directly controls or influences energy storage, cell growth and repair, reproductive function, and, most important, blood sugar levels.

Insulin “unlocks” a one-way door into cells so they can store or use nutrients. Insulin effectively stores all macronutrients—protein, fat and carbohydrates—but its secretion is most closely tied with carbohydrate ingestion.
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When we eat carbohydrate, it is broken down in our bodies into simple sugars and then absorbed into the bloodstream. This leads to a rise in the amount of circulating blood sugar (glucose).

To be optimally healthy, our blood glucose levels
must
be kept within a normal range—not too low, not too high. Remember, just as in the thermostat analogy, “normal” is pretty much synonymous with “healthy.” In the case of regulating blood sugar, your pancreas is the primary thermostat, and insulin is like your air conditioner, keeping blood sugar levels from remaining too high.

A rise in blood sugar is sensed by beta cells in the pancreas, which then secrete insulin into the bloodstream. Insulin signals cells in the body to pull glucose out of the bloodstream and move it into storage, bringing blood sugar levels back to a normal, healthy range. Elevated insulin levels also have a satiety function, reducing hunger.

Insulin’s management of blood sugar serves a very important function, as chronically elevated blood glucose levels are highly damaging to many body systems, including the liver, pancreas, kidneys, blood vessels, brain and peripheral nerves. Got that?

Once cells have taken glucose out of the bloodstream, that glucose can either be used for energy or stored for future use. The primary place to store glucose is in the liver and muscles, as a complex carbohydrate called
glycogen
. If stored in the liver, glycogen can easily be converted back into glucose and released back into the bloodstream when energy is needed. However, glycogen stored in muscle cells can’t be emptied back into the bloodstream—it stays there, to provide fuel for your muscles. (Which is good, because your muscles can do a lot of hard work!)

To begin with, a constant excess supply of carbohydrates will tilt your metabolic “preference” toward burning what’s most plentiful—sugar—when fuel is needed. If there is an overabundance of sugar, the sugar takes precedence over fat as a source of energy in many metabolic processes, and stored fat doesn’t get burned for energy.

If less fat is being burned for fuel, then it accumulates, and body fat levels tend to increase.

In addition, all that excess glucose poses a storage problem in the body. If there’s space available in the liver and muscle cells, they’ll happily uptake glucose. However, if those cells are already full of glycogen, they will politely decline any additional nutrition (essentially putting up a No Vacancy sign). When there is no room in the liver and muscle cells, the body shifts fuel storage to Plan B.

You will not like Plan B.

When the liver and muscle glycogen stores are full, the liver (and your fat cells) converts the extra glucose into a type of saturated fat called palmitic acid, which can then bind together in groups of three (with glycerol) to form
triglycerides
.

These two processes combined—the preferential burning of carbohydrate over fat for fuel and the creation of triglycerides—lead to increased body fat and increased triglycerides and free fatty acids in the blood, neither of which is desirable or healthy. And this pileup of sugar and triglycerides in the blood pushes another hormone, leptin, out of balance.

Summary: An “energy balance” hormone that is secreted primarily by fat cells and is released in proportion to the amount of fat stored. Leptin tells the brain how much body fat is stored and
regulates both energy intake and energy expenditure to keep body fat levels in balance. Overconsumption of nutrient-poor, supernormally stimulating carbohydrates leads to chronically elevated triglycerides and blood sugar levels, which promotes leptin resistance and an increase in fat storage, accompanied by greater insulin resistance.

Leptin is sometimes referred to as a “satiety hormone,” because higher leptin levels help to keep us full and satisfied. Leptin levels follow a normal daily cycle tied primarily to your eating schedule. Since you don’t eat while you’re asleep, leptin is pretty low first thing in the morning. This triggers the secretion of appetite-stimulating hormones and is one of the reasons we wake up hungry. When you’re done eating for the day (typically after dinner), leptin levels are higher, helping you stay full and satisfied until bedtime.

However, leptin’s primary job is to regulate your big-picture hunger and activity levels to help keep your body in “energy balance”—not too fat, not too lean. Body fat is not a bad thing—it’s what allows us to survive long periods of food shortage (or to not eat for a few days when we have the flu). But our bodies are pessimists.
Our DNA always expects, despite the surplus of readily available energy
right now
, that food will run out soon, and so the only way to survive this coming famine is to store some energy as fat.
It’s as natural as breathing.

As fat is a storage depot for energy, it is important for your body to have a way to measure how much energy (fat) is available at any given moment. Fat cells do this by secreting leptin, as a way to communicate to your brain whether you are too fat, too lean, or just right. Based on leptin’s critically important message, your brain constantly gives you subconscious directions, which drive your food-seeking behavior and physical activity levels.

If you have very little body fat—perhaps too little to survive a potential food shortage—leptin levels are low. The relative absence of leptin’s message tells the brain, “I don’t have enough body fat!” Your brain then tells you to eat more and move less, which serves to change your behavior until your body fat is within a safer range. You become hungrier (and probably eat more), your metabolism slows down (thanks in part to changes in your thyroid hormone levels) and you start to gain body fat.

As body fat continues to accumulate, leptin levels rise, and your fat cells start to send more messages to your brain—“OK, we’ve got enough energy stored now!” If that message is properly received (i.e., you are
sensitive
to the leptin message), your brain then tells you to increase your activity and makes you less hungry, so you move a little more and eat a little less, and don’t gain too much weight.

Although it’s much more complicated than this simple summary, this energy-balance system is naturally designed to keep your body fat levels “just right.” The trouble starts, though, when the foods you’re eating promote an unhealthy psychological response, leading to chronic overcarbsumption.

Shall we recap?

When you chronically overconsume food-with-no-brakes, it floods your system with glucose. With sugar in such large supply, it is burned first for energy—which means fat takes a metabolic back seat and accumulates. This leads to a buildup of triglycerides in the liver, and increased glucose and triglyceride levels in the bloodstream. But how does this lead to problems with leptin?

The excess glucose and triglycerides in the bloodstream make their way to parts of your brain and start impairing your brain’s ability to “hear” the leptin message. This leads to a condition called
leptin resistance
.

Leptin resistance is like a hormonal conversation gone haywire. Normally, when you’ve accumulated adequate body fat, your fat cells send a message (via leptin) to your brain that says, “Hey, we’ve got enough energy stored, so you should eat less and move more.” But when receptors in the brain and other tissues become less sensitive to leptin, those messages don’t get through. Your brain doesn’t hear leptin say that you’ve got enough body fat stored.

Which means your brain thinks you’re
too skinny
.

Imagine that your brain is blind, unable to see your chubby reflection in the mirror or the creeping number on the scale. It
needs
leptin to give it the facts it can’t see. So until the brain hears leptin say, “OK, we’re fat enough,” the brain is going to keep telling you to eat more and move less, to ensure your survival.

Remember, it’s pessimistic. And without that leptin message, your subconscious brain will continue to direct your behaviors as if you were too lean—despite the fact that you
know
you’re gaining too much weight.