Your Metabolic Thermostat
Weight loss is a very difficult undertaking as anyone more than a few pounds overweight can attest to. The reason that weight loss is so difficult and weight gain comes on so easily is due to a metabolic principle that I refer to as the “thermostat effect.” Just as a thermostat works to balance the amount of cold air and warm air that is pushed into a room to maintain a constant temperature, our metabolism has a built in “thermostat” that works to adjust the balance between the calories that are burned and consumed to keep your body weight constant. This metabolic thermostat works to keep our weight from dropping too low, regardless of the environmental conditions. Believe it or not, the thermostat also works to keep us from overeating and gaining too much weight. Durable weight loss does not come from eating fewer calories, it comes from re-setting your thermostat to a lower weight and maintaining this setting.
This theory stands directly against the widely accepted model of obesity that claims that weight gain is the result of eating too much and exercising too little. The medical community and popular press have embraced the idea that obesity is the result of gluttonous eating and sloth like habits. This belief has spawned an extensive network of programs designed to alter behavior through meticulous point or calorie counting, exercise programs, convenient portion controlled meals and even hypnotism targeted at blocking hunger. These programs uniformly fail, not due to the lack of discipline of the participants, but because the fundamental philosophy behind them is deeply flawed.
It is only after performing hundreds of gastric bypass procedures that I recognized the holes in the behavioral model of obesity. I have watched closely as surgical patients lost weight easily and permanently while others tried and failed through one form of starvation or another. The research that debates the validity of these two competing models of weight loss is extensive and complex, so please be patient with me over these next few pages as I try to explain why a short circuit in our metabolic thermostat is a more accurate model for obesity.
Let’s start with a simple fact – one pound of fat contains approximately 3,500 calories. It doesn’t matter if the fat comes from lard or vegetable oil, it contains 3,500 calories. This also means that in order to lose one pound of body fat, you must burn 3,500 more calories than you take in. Now, let’s look at how many extra calories a 50 year old man who weighs 400 pounds must eat, assuming he started at 150 pounds at age 15. Using the standard model of calories in vs. calories out, you’ll find that it takes less than 70 extra calories per day to cause someone to gain these 250 pounds over the first half of their adult life. One slice of bread contains 70 calories, so the 400 pound, 50 year old man that is judged by society to be a glutton and a sloth has committed the egregious sin of eating an extra slice of bread every day. This also assumes that if you have been able to maintain your weight over your adult life, you have done it by consciously altering your food intake to match your energy expenditure down to the last crumb, because even 10 extra calories a day will result in an extra pound being added every year.
The fact that anyone can manage to stay thin proves that maintaining an equal calorie balance is not a cognitive exercise but rather a subconscious one, just like maintaining a constant respiratory or heart rate. Since we must acknowledge that there are subconscious controls that impact the tight balance between calories consumed and calories expended, we can only assume that obesity is the result of an alteration in this control system.
Under starvation conditions (or during a diet), we typically lose a few pounds rapidly, causing our current weight to become several pounds below our metabolic thermostat’s set point. After a few weeks of starvation, our metabolic thermostat kicks in to try to remedy this abnormality. Many people assume that losing weight triggers our metabolism to slow down – this is correct, but only partially so. To get a complete understanding of why traditional starvation diets fail, we must look at the different ways our metabolic thermostat controls our calorie balance.
The first and most effective way to remedy the discrepancy between our starved weight and our metabolic thermostat’s set point is to release hormones that trigger our brain to seek out food. Many people think that resisting food temptations while on a diet is a matter of willpower and that their inability to resist the temptations of food is a sign of mental weakness. The situation is so much more complex than this! You are much less in charge of your ability to resist food temptations than you think. After a few weeks on a traditional starvation diet, your brain is flooded with hormones that are driving you to eat more.
Your brain will also release neurotransmitters that cause you to move slower and expend less energy. You will find yourself sitting down more often and dodging phone calls from your workout partner. In short, starvation will cause your brain to transform you from the willing, determined person that started your diet into a glutton and a sloth – and there is not much that you can do about it. Please don’t misinterpret this last statement – this does not mean that there is nothing that you can do about your weight – it only means that you cannot starve the weight off through traditional diets.
The best example of the behavioral changes that food deprivation can cause comes from the Minnesota Starvation Experiment, carried out between 1944 and 1945. In this experiment, healthy volunteers were forced to eat a very low calorie diet for almost an entire year and the physical and psychological effects were measured. The study was carried out primarily on conscientious objectors of the war who volunteered for the study as an alternative to military service. The subjects were thoroughly screened for any pre-existing medical of psychiatric conditions.
During the study period, depression, anxiety and severe emotional distress were observed. Also, the subjects exhibited an obsession with food and developed long, drawn out eating rituals for their meager portions. Often, the subjects were observed swapping recipes with each other and recalling their favorite meals or other events centered on food. The subjects also became extremely lazy, sleeping excessively and becoming more introverted. They reported that they all knew where the elevators were in the building and would avoid the stairwells as much as possible.
Many people assume that their ability to endure prolonged, restrictive diets is merely a matter of willpower, but the Minnesota Starvation Experiment reveals that our desire to eat is primal and powerful and will eventually overcome even the most disciplined minds. Just as willpower cannot be used to hold your breath to the point of suffocation, following a calorie restricted diet forever is impossible once your hunger drive takes over.
So, if traditional starvation diets will never work, what can be done to lose the weight and keep it off? The answer is to learn how to re-set our metabolic thermostat to a lower weight. The Pound of Cure diet was created for this purpose exactly.
Everyone’s thermostat is set to a different weight by a combination of both environmental and genetic factors. This explains why your sister-in-law who eats a dozen donuts weekly stays thin while you manage to gain a few pounds just from walking into a bakery. As you age, there are many events that can increase the setting on your thermostat. Pregnancy, processed foods, menopause, certain medications and an injury that results in a prolonged period of decreased physical activity can all set your thermostat to a new, higher weight. When your metabolic thermostat is turned up, you will become just like the subjects in the Minnesota Starvation Experiment – you will develop insatiable hunger and will avoid physical activity at all costs. You will be powerless to resist the additional pounds that you pack on as your metabolic thermostat drives your current weight up to its new, higher setting.
We’ve examined the changes in your brain and your body that occur when you starve yourself below your thermostat’s setting. Now, let’s look at the opposite situation, when you are overfed up to a weight that exceeds your thermostat’s setting. Although there are very few studies that examine the effects of overfeeding on humans, there are dozens of studies in rats.
When rats are overfed by using a feeding tube to deliver twice as many calories as rats typically consume, they gain weight. It is not surprising that they gain more weight than rats who are allowed to eat freely. This experiment alone is hardly ground breaking – the interesting results come after the feeding tube is removed and the rats are allowed to eat freely again. The overfed rats will move more frequently and naturally eat less than the rats who were allowed to eat normally during the entirety of the experiment. After a few weeks, the weights of the overfed rats will slowly drift downward to match the weights of the other group of rats. When a rat is overfed, its current weight is artificially driven above its metabolic thermostat’s set point. When this happens, the results are equal and opposite to those that occur after a period of starvation. The rats lose their appetite and begin to eat less. They also move more in an effort to burn additional calories and shift their body weight back toward the lower set point.
Figure 1 – Your metabolic thermostat
We see very similar changes in humans who stop taking medications that increase their metabolic thermostat’s setting. The best example is the temporary use of corticosteroids like Prednisone. Corticosteroids work to decrease inflammation and are used to treat conditions like Crohn’s disease and rheumatoid arthritis. When a patient is placed on these medications, they gain weight because corticosteroids work to increase your metabolic thermostat’s set point. Once the medications are stopped, the thermostat goes back down to its original setting, leaving the patient in an “overfed” state. The patient will lose their appetite and begin moving more frequently and the weight will naturally drift back down to the original set point.
Long term weight loss success lies in learning how to reset your thermostat to a lower weight. The Pound of Cure diet is different from traditional restrictive diets that limit your calorie intake and rely on self-imposed periods of starvation that will never result in durable weight loss. It is only by changing the content of your diet that you can hope to nudge your thermostat down to a healthier weight. This can only be done slowly, over time, utilizing a diet that is rich in nutrients and unlimited in portions and makes no attempts to thwart your hunger drive. Over the period of a year or even more, the excess fat will disappear as your thermostat is reset to a healthier weight.