Your body is a fat-storing machine–it’s really good at storing fat.
There are two main reasons it stores fat so well:
- To have energy beyond the amount of stored glucose, known as glycogen, you can hold in your muscles and liver (they can only hold so much), and
- To help quickly remove sugar from your bloodstream when you eat it. Sugar in your bloodstream is toxic—prolonged exposure to it can damage your heart, your nerves, and your kidneys. And because you can only store so much glycogen in your muscles and liver, you need that third, more flexible storage area to get sugar out of your blood and keep it from damaging other tissues in your body.
Sugar is energy. It’s like the gas in your car. When you eat it, your body either uses it immediately or stores it for later use in your muscles and your liver, just like some gas is used as you leave the station and some is stored in your gas tank. And by “sugar,” I mean carbohydrates. Everything from table sugar to tomato salad has some sugar in it.
But, your “tank” (muscles and liver) can only store a limited amount of glycogen—about a day’s worth. Glycogen is a pretty short-term energy strategy.
Now your brain is a huge consumer of energy. It is definitely your body’s gas guzzler—it uses 20% of your energy. And as you might imagine, your brain is pretty important in your daily life—everything from thinking about stuff to operating the systems in your body. What this means is that without another source of fuel—additional eaten sugar or another form of storage—your brain could quickly run out of gas.
You know what this feels like. We have a word for it—”hangry.”
So, we need to be effective storers of energy if we want to not just survive, but to function well. Unlike our car, we have a second strategy for long-term energy needs—we have a practically unlimited ability to store sugar as fat. The sugar that won’t fit in the tank can be stored as fat. Fat is a much longer term energy strategy.
Just because we don’t need long-term energy solutions now, doesn’t mean we didn’t used to. We have at times required the ability to go for long periods without actually eating food. This was important not only during our early days when we hunted for our food, but during more recent periods of famine. Living off of fat stores allowed us to survive when food was scarce.
While you can store about a day’s worth of energy in your muscles and liver, an average person (who is not overweight) can store around a month’s worth of energy as fat. That gave us a lot of leeway for finding food.
And you can store much more energy than that. In 1965, a man named Angus Barbieri, who weighed 455 pounds, fasted for 382 days—over one year—until he weighed 180 pounds. All he consumed during that period was a multivitamin and potassium and sodium supplements.
I’m not suggesting that anyone do this (he was under very strict medical, sometimes in-hospital, supervision), but the point is, our bodies can store energy for periods of very long time without eating.
This is why it’s so important to reduce the amount of sugars and refined carbohydrates, things like bread and pasta, in your diet, and why people who eat fewer carbs also eat more fat in their diet without gaining excess weight.
Sugar and other refined carbohydrates introduce large doses of sugar into your bloodstream quickly. Blood sugar is a signal to your pancreas to produce insulin. Insulin is a hormone that tells your cells to open up and let sugar in to be converted to glycogen and stored in your muscles and liver. When that’s full, the excess sugar is converted to triglycerides and stored in your muscles and fat tissue to be used later. If you don’t eat a lot of carbohydrates, you can use this energy pretty easily. If carbohydrates are a regular and large part of your diet, it’s much more difficult.
This can have a negative cascade effect if it gets out of control. While that is a little bit beyond what we’re talking about here, suffice to say, the more sugar you eat, the more insulin you release.
Because insulin’s job is to help store energy away, the more sugar you eat, the less access you have to stored energy—while it is insulin’s job to store sugar, it is also its job not to let it out.
That means you’re going to store that excess sugar as fat and when you need energy, you’ll get hungry for more sugar to fill the energy demands that aren’t being filled by the sugar that’s locked away because you’ve got too much insulin circulating in your blood for loo long.
The reason our predecessors didn’t have this problem was that they didn’t have refined carbs. As a result, their body was very sensitive to insulin, requiring very little to do its job (your body can get quite tolerant to insulin, just like alcohol). It came in, performed its function, and was cleared out. When energy was needed, it was accessible.
Unlike sugar, fat does not trigger a release of insulin, which is part of the reason why people who eat fewer carbs can eat more fat in their diet. Not only are they replacing one energy source with another, they’re not trapping it away.
It doesn’t mean you can eat an unlimited amount of fat. Your body still does have mechanisms for storing fat in your muscles and fat cells. But because dietary fat does not trigger insulin, your access to the stored energy isn’t limited by circulating insulin, and you will likely not find yourself as hangry when your body needs energy. You won’t need to take in more energy, you’ll simply use what you have stored—it won’t be locked away by circulating insulin.
So while we’re really good at storing fat for really good survival reasons, it can cause real problems if we’re eating too much cheap and easy forms of energy like sugar and carbs.
We also have strategies to moderate that fat storage which involve keeping as much sugar out of our body as we can and using, maybe surprisingly, more dietary fat as a form of energy.
While we’re good at storing fat, we’re also good at using it. It’s dense and our body knows what to do with it, especially if it’s not conditioned to use sugar. Sugar is the path of least resistance for our bodies. If it’s there, we’ll use it. But we do get a fair amount of our energy from stored fat. And the more we allow our body to use fat as energy, the better we get at metabolizing it, burning both the excess fat we might have stored and the fat we consume for energy.
By steering away from “carb loads” and towards fats and whole foods, you can mitigate your body’s innate ability to store fat for a rainy day and turn yourself into a fat-burning machine as opposed to a fat-storing machine.