When I first discovered low-carb eating a few years ago and found that I could lose weight and improve my health without eating less or going hungry, I started telling people, “Calories are irrelevant!” I didn’t really believe it, though. The research I was reading, and my own experience, showed that calories weren’t as important as the amount of carbohydrate in the food, but I assumed calories still mattered somehow under the surface. I declared their irrelevance as a conversation starter, as a way to get people to question their assumptions, but I never fully meant it.

After all, we all know that every calorie we consume has to be burned in exercise or stored as fat, right? Has any other assumption been so firmly accepted as fact in modern society? It affects most of the meals we eat; how our food is processed, packaged, and marketed; and how we look at others. The fat guy eating a triple cheeseburger is surely a slob and a glutton; the one who orders a baked potato is conscientious and reliable.

As I’ve learned more about human biology, however, especially fat metabolism, I’ve started to realize I was more on target than I knew. The fat cells are not open cubbyholes on a wall, where extra fat molecules can be tossed and then retrieved later. A fat cell is more like a room with a whole bunch of doors that exit onto the hallway that is the blood stream. Each of these doors has a different type of lock, and the keys that open them are hormones and enzymes. The doors are also very small, and have funny shapes, so even when the right key comes along and opens them, only certain things can get in or out. The doors also only allow traffic to pass in one direction, and which direction is determined by which key is used to open them.

Now to back up a little bit. Fat is stored and transported through the blood stream as a triglyceride. You’ve probably heard of these evil little buggers in relation to cholesterol. A triglyceride is made up of three fatty acid chains attached to a glycerol molecule. This big structure can’t get through the doors of the fat cell, so it has to be broken down into its parts—fatty acids and a glycerol—so the parts can be transferred inside. Once inside, they are put back together for storage. To get them back out—to “burn” fat—they have to be broken down again, passed through the doors, and put back together.

There are several different hormones that act askeys for these doors. The biggest is insulin, which opens the door of fat cells to allow incoming transfers only. When the insulin level in the blood is high, it tells the fat cells to reach out and grab triglycerides, break them apart, pull them through the doors, and put them back together inside. Without insulin to trigger this action, the doors stay closed and fat can’t be stored, which is why Type I diabetics can waste away no matter how much they eat.

Everything in the body has a balancing counterpart, and insulin has several: glucagon, adrenaline, growth hormone, and others. These open the fat cell doors in the opposite direction, outgoing. When these hormones outnumber insulin in the blood, the fat cells start breaking down triglycerides, pushing them through the doors, and putting them back together in the blood stream, where they can be transported to the muscles or organs which use them for fuel.

Notice that none of this has anything to do with how many calories are being eaten. If insulin is dominant, the exit doors on the fat cells will be closed, even if the person is starving. If insulin is low and glucagon is high, the entrance doors will stay locked, no matter how much fat is floating around in the blood looking for a place to go. This is why we all know some people who can eat like horses and not gain weight, and other people who seem to always be dieting and only getting fatter. It’s not that the skinny glutton is secretly bulimic or skipping meals in private, or that the fat guy is secretly stuffing himself or needs to exercise more. It’s because their hormones are telling their fat cells to do different things: in the skinny person, to keep the entrance doors closed; and in the fat person, to cast them wide open.

So, how do we use this? How do we lower our insulin level and raise the level of counterregulatory hormones? The simplest, fastest way is to reduce the amount of carbohydrate we eat. Insulin is created in direct response to carbohydrate, because aside from controlling fat metabolism, it also controls the amount of glucose in the blood stream. Excess sugar in the blood stream is toxic, so keeping glucose levels normal is far more important to the body than whether we gain a pound or two. Eat more carbohydrates, produce more insulin, kick open more entrance doors to the fat cells. Eat fewer carbs, less insulin is needed, the entrance doors on the fat cells stay closed.

Okay, so now we’re on a low-carb diet, keeping insulin at a healthy, stable level. So how can we increase the levels of the counterregulatory hormones, to start kicking the exit doors on the fat cells open? This happens automatically to some extent, which is why people who cut back on sugars and starches (which everyone knew was the way to lose weight until the 1960s) almost always lose weight. Some glucagon is always being produced, but in the high-carbohydrate eater, it’s overwhelmed by the flood of insulin. Getting rid of the insulin surge gives the counter hormones a chance to work.

The production of counters like adrenaline and growth hormone is suppressed by high levels of insulin, so these typically rise when insulin falls. There is some evidence that heavy exercise promotes the secretion of growth hormone, so that may help as well, and may help explain why exercise is enough to spur weight loss in some people. If one’s hormone balance is just barely leaning toward the insulin side, some running or weight lifting could tip that balance back the other way. For people in whom insulin is flooding the system, however, even extreme amounts of exercise may have no effect if insulin levels are not brought down by carbohydrate restriction.

That’s the system in a nutshell—greatly simplified, I admit. It explains why some people struggle with obesity while others gobble their way to thinness; and it shows us what to do about it. I’ve been low-carbing on-and-off for several years now, and one thing I can say for sure about it: It works every time I do it. Unfortunately, I’ve only stuck with it for a few stretches, so I’m not as lean and mean at this point as I could be. I’m back to it now though, so I’ll be writing more about my progress in the future.

References:

• Good Calories, Bad Calories, by Gary Taubes
• The Protein Power Lifeplan, by Drs. Mike and Mary Dan Eades