Our appetite control system not only regulates our food intake in the short term, but our weight over the long term. It does this by sensing the amount of fat or adipose tissue we have stored. The body weight and amount of fat stores that our body tries to maintain is called our set point. You can think of set point like a thermostat for weight. If our weight drops below the thermostat setting, it compensates by increasing appetite and slowing metabolism until we regain the weight.
The same thing happens when we gain weight. We feel fuller and our metabolism speeds up until we lose weight back to our set point. Given that for some people, weight steadily rises, you may be wondering, how can it be that we have a set point? Why do these compensatory responses kick in to help us lose weight? Much research now indicates that in obesity, our bodies are no longer functioning normally. The set point ratchets up, and our body fights hard to defend this new set point. In fact, our set point can steadily increase upwards or slide downward. It is not fixed. Let's look at two scenarios.
The first at our set point where body weight is normal. When a person with normal body mass index is placed on a very low calorie diet, he or she will likely lose weight. But once allowed to eat at will, our energy balance system kicks into drive weight back to our starting point. The same happens when we're intentionally overweight. Once allowed to eat at will, we subconsciously lose appetite and our brain speeds our metabolism until we lose weight. In the case of obesity, set point rises in proportion to our body fat. The same defense has tried to maintain the new hire set point.
So, even if weight loss is hard-earned by following a diet, it becomes hard to maintain that weight loss. Our body acts like we're starving, even though we may be overweight. While often people who are overweight feel they may lack the discipline to lose weight and keep it off, science is suggesting that obesity is a disease where our control systems become abnormally regulated around a higher set point and the body doesn't function normally.
The main takeaway is that even though we focus so much on how our eating and exercise behavior controls how our body functions, the reality is that the way our body functions is what controls our eating behavior. While we view regaining weight and reverting back to being overweight as failure, what is really happening is our body is fighting what it perceives as the threat of starvation due to a higher set point. It's still frustrating, but understanding why this happens can help you understand how to work with your body to successfully lose weight and keep it off. Over the course of the following weeks, one of the things we're going to focus on is how our environment, not just our food, but also our habits can affect our set point to lead to obesity. Targeting these factors will help get to the root cause of obesity so that you can create an individualized plan for managing weight long term.
It's common to observe that some people can eat hardly anything and yet their weight stubbornly claims, while others seem to eat nearly everything and still maintain their weight. Why is that? How much of our body weight is locked or genetically determined? And how much is in our control?
Through an explosion of genetic research, mostly over the past decade, scientists have found common genes that account for approximately 20 percent of the variation in body mass index across the population. Each of these genes only makes a tiny difference in our body weight and we each inherited a different combination of these genes. Our mix of genes ultimately determines a small proportion of body weight. This is the part over which we have little control.
What is the function of these genes? Interestingly, they mostly correspond to functions in our brain, influencing areas that play a role in our appetite and energy control systems. Some of these genes for example, may affect the reward or pleasure we get from food. Others may determine how quickly we send hormones that tell the brain we are full. Depending on the combination of genes we get, our experience with food may be different, how we taste food and the pleasure we get from it may be different. It may be easier or harder for you to avoid chocolate cake or stop eating even when you know you're a full than it is for me. What that also means, is that we each have a different predisposition to obesity. It means that obesity isn't one disease, there are many subtly different types of obesity caused by different subsets of these genes.
While that may be surprising, it's really no different from what we're learning through genetics about other common diseases such as diabetes, high blood pressure, and depression. Eat is not one disease but many similar diseases, which explains why each person responds differently to medications for these conditions. Since the genes discovered to be associated with body weight control our susceptibility to obesity, the drivers that lead to becoming overweight or obese are different from person to person.
As a result, the diet or any other approach to weight loss for that matter that works for one person, may not work for another. There is no one size fits all answer to weight loss. Our goal is to help you find what unlocks your success. Since the genes that have been discovered to affect our body weight control only a small proportion of the differences seen in body mass index, the good news is that we can determine most of our body weight through choices we make and through shaping our environment. In other words, most is in our control. The fact that our genes haven't changed much since the 1980s, but rates of obesity have skyrocketed, reinforces this idea. With that background, let's dive deeper into the changes in our food as well as other changes in our environment that have been making managing weight so challenging, and what we can do to manage obesity.