The Set Point, the Settling Point, and What You Can Do About It
In my last post I discussed the complexities of obesity and some of the metabolic and neurobiological effects that cause weight gain and maintenance of a higher body weight. I received a question from my longtime friend and follower, Hayley, about the defense of weight. She asked, “Once an obese person loses weight does their body ever reset again? Or will their body try to reach its highest weight for the rest of their lives?”
These are great questions and I’ll answer them out of order. There seems to be no definitive answer for the second question so I’d like to go over a couple of the predominant theories in the field of body weight regulation to offer some insight on that question.
Set Point Theory
The set point theory focuses on biological control of weight and fat mass and posits that there is a control system (genes and hormones from the gut, brain, and adipose tissue) dictating how much fat someone should carry, which varies from person to person. I’m going to focus on fat (adipose tissue) mass because this is much more malleable and what we’re generally talking about when we talk about weight loss. Fat mass regulation is controlled by both sides of the energy balance equation (intake and expenditure) and the set point theory suggests that changing one side of the equation will lead to corresponding changes in the other. For example, if you reduce intake, the body will reduce expenditure to try to maintain fat mass. That is, the body will “defend” its highest sustained weight, ultimately thwarting your best efforts to lose weight and keep it off. However, it’s important to emphasize that this is a theory that has not been proven and isn’t accepted by all obesity scientists and physiologists. Indeed, the set point theory may be too simplistic because it does not explain why the world’s set points have gone up over the past 50 or so years and is contradicted by data that demonstrates that starvation and subsequent refeeding can result in even higher body and fat mass than the initial weight (that is, the body overcompensates after extreme weight loss).
Settling Point Theory
That brings me to the idea of the settling point theory, which focuses almost entirely on the environment and human behavior. This is the idea that body fat levels will “settle” into a given range in response to the habits that a person practices. So, if food is highly available and you don’t have to work very hard to get it (i.e. America), your body fat may “settle” at a higher point. Conversely, if you are put into an environment of low food availability and high physical demand, your fat stores will settle at a lower point. There are data to back up this idea: the current food environment supports increased energy intake due to the abundance of extremely tasty, calorically rich food that is served in large portions coupled with the fact that we have to do very little physical work to live (thank you cars and washing machines). However, this theory doesn’t take into account any biological control of weight, despite the fact that numerous studies have shown that biological regulation of fat mass exists. For example, in the Minnesota Experiment that I previously mentioned, severe caloric restriction resulted in marked weight loss that plateaued at a certain point (support of the settling point theory). However, when subjects were allowed to eat whatever they wanted, they didn’t simply resume their old habits and slowly regain the weight. Instead, they regained weight and fat mass rapidly, indicating that they were over-eating in an attempt to restore fat and lean mass. They did, in fact, restore mass and then some. This suggests that there are active controls within the body to increase fat mass (i.e. evidence to support the set point theory). Furthermore, there are data that support the notion of changes in energy expenditure during times of starvation and overfeeding, indicating that the body is attempting to adapt to changes in intake (adaptive thermogenesis).
While both the set point and settling point theory have their shortcomings, it may be most reasonable to consider them together and recognize that biological control of intake and expenditure exists, but these can be overrun or attenuated by an obesigenic (obesity causing) environment. So, to answer Hayley’s second question: I haven’t seen data that shows, specifically, that people will always regain weight back to their exact highest weight and I don’t think everyone will. Further, as with everything with humans, there is likely a large amount of inter-individual variability and some will struggle with maintaining a healthy weight more than others. So, while I could find no clearcut answer, hopefully the two theories I presented along with the physiology I described in my previous post will give you some ideas of how this all works.
Now on to the first question: I have found some evidence/hypotheses to suggest that the set point can be reset. Here are a couple of tips that I have found:
Professor Jim Hill at the University of Colorado suggests that our physiology works best at high levels of physical activity. Physical activity is likely to improve the body’s ability to assess its need for nutrients (and eat accordingly) as well as partition dietary fat to be burned instead of stored. So if you’ve lost weight, you’ll likely need to do a fair amount of exercise to keep that weight off. The good news is that every other system in your body (other than those regulating your fat mass) will thank you. The Physical Activity Guidelines for Americans recommend that 60-90 minutes of aerobic activity/day may be necessary to avoid weight regain, but remember: any amount is better than none.
- 10% rule
One hypothesis for effectively losing weight and maintaining it is to use the 10% rule. The idea is that when you lose more than 10% of your weight, your body starts to resist by reducing its energy expenditure and increasing hunger cues in order to “defend the set point.” However, losing only 10% or less at a time may not trigger these responses and, thus, could lead to sustainable weight loss. One approach, as outlined by the online weight loss course at the Beth Israel Deaconess Medical Center at Harvard. After 6 months of maintaining that new weight, you are advised to lose 10% of your new weight and so on until the goal weight is reached (which is when you’ll really need to focus on the goal of 60-90 minutes of activity/day). I like this approach because it allows you to set realistic and attainable goals. For example, if your starting weight is 200 lbs, losing 20 pounds (and then 18 and so on) is easier to stomach than a goal of losing 50 all at once. And while I like the sound of it, I have yet to find any clinical trial that has tested this hypothesis. I’ve seen this 10%-weight-loss-6-month-maintenance-phase recommendation all over the internet, though there are never any accompanying citations (if anyone has seen these data, please send them my way). I’m wondering what the 6-month weight maintenance timeframe is based on. Perhaps something as short as 6 weeks or a few months would be equally beneficial. Overall, though, it’s best to think of weight loss as a journey instead of just a destination (sort of like life) and work through it at a slow, reasonable pace, learning new habits and lifestyle changes that are sustainable along the way.
Hopefully I’ll be able to find some kind of hard evidence on this “10% step down” approach. If I do, I will update this post with that information. As always, please don’t hesitate to offer insights and ask questions!