- Let me introduce you to Amanda. You're just meeting her for the first time but chances are you're already making assumptions about how much she eats and how little she exercises because she's obese. But I'm about to show you that there's much more than meets the eyes when it comes to obesity. There are lots of Amanda's out there and they need treatment. Maybe you're one of them or maybe you know an Amanda. It's time to act on obesity. But in order to do so effectively, we need to understand obesity. It's generally accepted that body weight is determined by a pretty simple formula. We call it the energy balance equation and it works like this. If the number of calories that you consume equals the number of calories that you burn, your weight remains the same. If you consume more than you burn, you gain weight. And if you burn more than you consume, you lose weight. Most people think that those of us who properly manage our energy balance remain lean.
Whereas those of us like Amanda who eat too much and exercise too little become obese. We view obesity as a lifestyle choice and the cure for it is simple, eat less and exercise more. This may sound logical but it's wrong. Let me explain. First, let's talk about set point. No, I'm not talking about the point in a tennis match when one player is about to beat the other. I'm talking about a theory that says that no matter what you consciously want your weight to be, your brain has its own sense of how much body fat it should have on board. And it has a complex system in place that very precisely regulates your energy intake and expenditure to keep you within a so-called set point range for body fat. So that whole energy balance equation, it's not something that you control voluntarily. Your brain regulates your calories in to your calories out for you.
For your brain to do this, it needs to know how much energy you have on board at all times, and it knows this by listening to hormones like leptin, which is made in your body fat. You can think of it like a car. Leptin is the gas gauge that tells your brain how much gas is in your tank. But leptin is just one piece of the puzzle. You've got a whole bunch of other hormonal signals and senses that are involved too. Your bones, muscles, pancreas, liver, GI tract and sensory organs, they all play a role, communicating with your brain to give it the information it needs to do its job. But that's more detailed than we need for this conversion. The point is that you have a complex system in place that regulates you to within a set point range for body fat. So what happens if Amanda decides to lose weight by going on a diet. After all, people with obesity should eat less, right? Here's what happens. She loses weight but her hormone levels change. Her brain hears this, and it starts acting to restore whatever body fat she's lost.
She feels hungrier, and although she doesn't know it, she is also burning fewer calories than before. You see set point is usually a one-way street. Once it's been elevated the brain works to defend it, just as vigorously as it would a lower set point. Amanda's brain doesn't know that she needs to lose weight.
It only knows to defend her current set point. Back to our car analogy. Amanda can't help but look for a gas station to refuel when she sees that her gas gauge is low. At the same time she becomes more fuel-efficient burning less energy than before. This might explain why treating obesity with diet and exercise so often fails to produce the desired results. It's sort of like telling Amanda that she needs to be a more careful driver when the real problem is that she needs a mechanic to fix her car. Okay. So if we've all got this complicated system in place that prevents us from losing weight, why doesn't it also protect us from gaining weight and developing obesity in the first place? How can we explain the obesity epidemic? Getting back to Amanda, why did she develop obesity? The answer is that it takes a perfect storm to cause an obesity epidemic like the one we're seeing now, and it's our modern environment that places us and Amanda directly in the path of that storm.
Well, there's no single cause for the rising rate of obesity. Changes to the chemical and nutrient content of our food, the so-called western diet, a decrease in physical activity, increased levels of stress, inadequate and disrupted sleep, and more widespread use of medications that promote weight gain, all play a role. Our unique genetics and developmental histories cause each of us to respond differently to these elements of the modern environment, and some of us, like Amanda, respond by sending hormonal signals that elevate our set point for body fat. It's not that Amanda's system has stopped working. It's just that it's working to regulate her to a set point that's too high. So you can think of obesity as a biological response to the modern environment, a disease where the body dis-regulates to a body fat set point that is too high. Back to our car analogy. The size of Amanda's gas tank has expanded so she carries around too much fuel.