March 22, 2010
The Faulty Metabolism Myth
By Barbara Berkeley
“Why can’t I lose weight? There must be something wrong with my metabolism. “
This question and its seemingly logical answer must be among the most commonly stated beliefs of overweight people. But an answer that appears to be correct is not necessarily so simply because it has been stated repeatedly. As long as we keep asking this question and answering it in the same way, I believe we will not move an inch toward solving our obesity problem.
What if we looked at this question in an entirely new light, starting with a different kind of assumption? What if we began with the fact that the act of trying to lose weight intentionally is most likely an unnatural behavior for humans.
Why do I say this? Until very recently, there was arguably no time in man’s history when he would have thought of forcing his body to give up fat. Since humans lived close to nature, their relationship to food was more like that of other living creatures out in the wild. Fat storage, if it occurred, would have been beneficial, an insurance for lean times. There are very few lions on weight reduction plans.
The evidence for the unnatural nature of forced weight loss can be seen in our body’s response to calorie restriction. When we stop eating, our body does not just start happily burning fat. What it actually tries to do is to avoid losing weight. It does this by going into a sort of “economy” mode. To better understand this, imagine a situation in which you were cash poor with a cold winter approaching and a full tank of heating oil sitting in your backyard. Eventually, the cold sets in. You have that tank of oil, but you’d rather not use it since you are facing a winter of uncertain length. So you wisely decide to go into economy mode. You turn down the heat in your house and wear sweaters instead. You close off some rooms rather than burn fuel to keep them warm. You wait and hope that winter will pass. Meanwhile, your storage tank stays untouched, a hedge against true emergency.
This is exactly what your body does when you try to lose weight. Your genes don’t know that the food shortage they are experiencing is called “Weight Watchers” or “Jenny Craig.” They only know that they are suddenly facing a famine. Ancient responses shift the body into economy mode, dialing down the energy used for heat (the reason many dieters feel cold) and slowing down less vital processes. We call this “lowering the metabolism”, but basically it is the body’s attempt to keep weight stable during a food crisis.
Doesn’t the body want to rid itself of harmful fat? Paradoxically, the answer seems to be no. There is a perplexing propensity for the body to ignore its fat, almost to fail to realize that it’s there. Overweight people experience this every day when they deal with elevated levels of hunger. Why should the body continue to generate strong hunger signals when it is full up with fuel? The answer appears to lie in a disconnect between fat and the brain. Signals which should tell us that we have enough stored fat and that we should stop eating, simply fail to reach their mark. Something inherent in the very process of gaining weight acts as a disruptor to the normal signals that control fat and appetite. When it comes to weight loss, the body seems relatively determined to avoid burning its stored calories unless it is really pushed.
We are taught that the fundamental truth of weight loss is: burn more calories than you take in and you will lose weight. We are told that this is an immutable law of physics and that if it isn’t working, we must be doing something wrong. But all dieters know that this central tenet of weight loss is simply wrong. Adding more exercise often doesn’t lead to weight loss, nor does restricting calories. What is the problem here? The answer is quite simply the body’s ability to change the game by shifting into economy mode. This is maddening for dieters who often feel unable to lose an ounce when they cut back on food. But that problem reflects a simple truth: when you eat less, your body will run on less. A lot less. This is the beauty of our construction, a metabolic balancing act that allowed us to survive for millions of years. Yes, it’s frustrating. But here’s the good news. A solid understanding of this bodily behavior can help us figure out how to get around the problem.
In my experience, the biggest impediment to successful weight loss is something I call “calorie summarizing.” Americans are hooked on calorie theory, which is peculiar because calorie counting is nearly impossible and doesn’t work very well at all. But more on that another time. When people diet, they tend to look at days or weeks as a block. At the end of each block, they summarize what they ate. They see that, when the days are lumped together and on average, they ate far, far less than what they had been eating before their diet. They exercised far, far more. According to prevailing calorie theory, this should guarantee weight loss. Then they get on the scale. Shriek! They’ve lost a couple of ounces, or nothing at all. They throw up their hands and let out that eternal wail: “There’s something horribly wrong with my metabolism!” Often, they abandon their attempts to lose weight. How could they possibly succeed when they are so metabolically challenged?
But what has really occurred? Far from being metabolically flawed, their bodies have simply been doing their job, protecting their clients from the ancient threat of famine. From the point of view of the dieter, the problem was an inconsistent attempt to “scare” the body into using its stored fuel. On one day, this dieter ate more because she’d been good on another. Because she was so strict all week, it seemed fine to have that piece of birthday cake or that dinner out. Because the week’s total calories were lower than they had been, it seemed fine to have a treat here and there. In doing this, this dieter played right into her body’s hands. She gave the body just enough to get by in economy mode and too much to force it into significant fat burning.
A terrific study that appeared in the New England Journal of Medicine a few years ago supports this hypothesis. In this study, researchers compared average weight losses after one year on a number of different diets, including Atkins, Weight Watchers and the Zone. They showed that the average loss was quite small, just a few pounds. Initially, that looked pretty discouraging. But on closer inspection, researchers noted that not every dieter was average. Some actually gained weight, while some lost very large amounts. What differentiated them? In a stroke of brilliance, the researchers decided to look at their data through a new lens. They asked each subject how consistently they had followed their diet on a scale of 1 to 10. What developed was a perfect curve, the same for each and every diet that was studied. Weight loss began to occur at compliance levels of 5 or better. The largest amounts of weight loss were seen in those people who had been almost perfect in following their diet plan.
It probably matters very little which diet plan you follow as long as you don’t try to alter or make up the rules yourself. What seems to be fair, what seems to be scientifically correct, what seems to make sense, is often not the case during weight loss. What is the case is that your body will economize and run itself on less until you force it to do otherwise. Consistency, toughness and sticking with the plan – not just most of the time, but 90-100% of the time – are the behaviors that work. We must respect the fact that we are asking our body to do something it would rather not do. All the diet commercials in the world can tell you how easy it is, how you can lose weight without really dieting, how you can do it without giving up the foods you love. None of these assurances provide a hedge against the facts of life.
Please note that this particular post is not a maintenance post. While consistency remains very important in maintenance, some degree of off-plan eating can be offset by exercise. This is not the case during weight loss. Unless you are very big (people with lots of fat to lose will generally lose weight with less effort, at least at first), complete consistency is the key. Now you know why. If you have been trying to lose weight and have been bemoaning your slow metabolism, try rededicating yourself to the project by assessing your success from moment to moment rather than summarizing calories over time. Keep food records and measure yourself by how well you stuck to your guns each and every day. Convince your body that there is serious and ongoing food shortage in its environment and it will burn fat to take care of you.
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