What does science say about set point theory?
Set point theory is the idea that your body has an innate weight range that it tries to maintain. And everyone's set point is unique to them.
According to this theory, if you’re losing weight, your metabolism slows down, and you feel more hungry to help make sure you stay within your range.
On the other hand, if you overeat, a feedback mechanism ups your metabolism, and your hunger signals slow down, helping to keep you from gaining weight as easily.
But weight management is a complicated topic — and set point theory is just one of several theories that scientists have discussed.
In this article, we’ll look at the evidence for and against set point theory. We’ll also explore what it might mean for weight management.
What does the research say?
First, we’ll look at some evidence that supports set point theory. Then, we’ll cover the arguments against it.
Arguments for set point theory
The idea of a set point for weight mainly comes from animal studies.
In the 1970s, scientists discovered that rats gained weight if they were overfed with a high-fat, high-sugar diet.
Once the rats went back on their standard diet, their bodies self-regulated, and they returned to their original weights.
The opposite happened too: If the rats lost weight on a calorie-reduced diet, once they returned to their standard diet, they went back to their original weights.
Some scientists used these findings to develop the theory of a natural set point for body weight.
But people aren’t lab rats. And scientists don’t fully understand the mechanisms behind weight loss in humans. That’s why experts still work with theories.
Proponents of set point theory have also taken the following points as indications of biological weight control in humans:
Hunger hormones like leptin help regulate your appetite, depending on how much you’ve eaten.
Advocates of set point theory argue that this regulation might maintain your set point weight. They say that for every 1 kilogram of weight lost, your appetite increases, making you take in an additional 95 calories per day.
Arguments against set point theory
One of the main issues with set point theory is: If we have a biological feedback system that regulates our body fat, why do most people in Western countries gain weight throughout their lives?
For instance, the average weight gain for someone in the United Kingdom is 6.7 kg over 10 years.
It's thought that your set point can be “overridden,” and your set point range can increase accordingly.
Also, scientists know that rates of obesity are linked to a range of factors, with the food environment playing the biggest role — not individual behavior.
In other words, factors linked to differences in weight include social class, income, stress, and where you live. All of these affect whether you have easy access to healthy food.
This suggests that your set point (if it does exist) can change in response to your environment.
But weight management is very complicated, and there are many aspects that scientists don’t yet understand.
This may be obvious, but set point theory is just that — a theory that some scientists believe in.
Let’s look at some other theories about weight management.
Settling point theory
Settling point theory suggests that you can have more than one steady body weight state. These are “settling points.”
Imagine a lake or another natural body of water. It continually settles at different levels according to environmental conditions.
So, rather than believing that an active mechanism is working to maintain a particular weight, proponents of this theory believe that body weight settles depending on various factors.
Some might include your genes, your environment, your diet, and your lifestyle.
They also think that your settling point can change over time.
Dual intervention point model
The dual intervention point model proposes that your natural body weight has an upper and lower boundary — not a single set point.
Advocates suggest that we developed these upper and lower weight boundaries for evolutionary reasons.
In other words, if your weight fell too low, you’d be at risk of starvation. If it rose beyond a certain point, you’d have an increased risk of being eaten by a predator.
According to the dual intervention point model, biological mechanisms kick in when we’re close to the upper and lower boundary.
The rest of the time, your body weight can fluctuate quite freely between these boundaries.
The bottom line is: We don’t fully understand what factors influence our body weight.
And if each of us does have a set point, it may be overridden by today’s food environment.
Set point theory and weight management
The evidence so far suggests that even if a set point does exist, it’s easier to gain weight than to lose it.
This might be because the main function of leptin — the primary hormone that controls appetite — is to defend the body against fat loss. In other words, leptin makes you feel hungry if you take in too little energy.
But if you eat more than your body needs, the mechanisms that reduce appetite aren’t as powerful.
We can see this in the famous Minnesota starvation study from the 1940s. During 6 months of semi-starvation, the participants lost 66% of their initial fat mass.
When allowed to eat freely again, they regained 145% of their pre-starvation fat mass. Put simply, they “overshot” and ended up with more body fat than they started with.
There may be an evolutionary reason for a set point that’s easier to increase than decrease. For most of human history, food scarcity was a much bigger problem than having access to too much food.
We have biological signals that preserve our body fat levels by reducing our resting energy expenditure. These signals also generate powerful feelings of hunger that compel us to eat.
When is your set point set?
Even people who believe in set point theory disagree about when this point is established.
Some experts suggest that it’s hardwired into your DNA, while others believe that it may be influenced by the amount of fat in your mother’s body while you were in the womb.
It’s important to remember that these are just theories — there’s no solid evidence for one or another yet.
And of course, not all scientists agree that set point theory is correct. There are no robust studies in humans to prove it.
Right now, scientists simply don’t know enough about how and why we gain or lose weight. Theories give us a framework for speculation based on the little evidence we do have.
Can you change your set point?
According to set point theory, it may be possible to change your set point — despite your environment.
The theory suggests that if you gain weight slowly over time, this moves your set point up. If you slowly lose weight, this shifts your set point down.
There’s also some evidence from animal studies that weight loss surgery can reset your set point. For example, after surgery, mice maintain a new, lower body weight without excessive hunger.
But we need more research to test whether this is true for people.
With the ZOE program, you’ll get personalized advice to help you find the best foods for your body.
Set point theory is the idea that your body has an inherent weight that it tries to keep up.
But it’s just one of several theories. We don’t fully understand how body weight is regulated in humans.
Overall, it seems easier for most people to gain weight in the long term, rather than lose it. For that reason, rates of obesity are increasing with each new generation.
Some environments and food cultures likely promote weight gain.
If set point theory is correct, these environmental influences may be overriding your set point.
But weight maintenance is a complex topic, and scientists need to do more research to understand exactly how it works.
If you’re trying to lose weight and finding it challenging, know that you are not alone.
The theories we’ve discussed in this article may be of interest or a comfort and help show how many factors are at play when it comes to weight loss.
Differences in genetic and environmental variation in adult BMI by sex, age, time period, and region: An individual-based pooled analysis of 40 twin cohorts. The American Journal of Clinical Nutrition. (2017). https://pubmed.ncbi.nlm.nih.gov/28679550/
Exercise and weight loss: The importance of resting energy expenditure. (2015). https://www.health.harvard.edu/diet-and-weight-loss/exercise-and-weight-loss-the-importance-of-resting-energy-expenditure
Fatness and fitness: Exposing the logic of evolutionary explanations for obesity. Proceedings B. (2016). https://royalsocietypublishing.org/doi/10.1098/rspb.2015.2443
Genetic and environmental contributions to body mass index: Comparative analysis of monozygotic twins, dizygotic twins and same-age unrelated siblings. International Journal of Obesity. (2009). https://pubmed.ncbi.nlm.nih.gov/19030007/
Is there evidence for a set point that regulates human body weight? F1000 Medicine Reports. (2010). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2990627/
Leptin. (2018). https://www.yourhormones.info/hormones/leptin/
Maintenance of lost weight and long-term management of obesity. Medical Clinics of North America. (2018). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5764193/
Nutrigenomics of body weight regulation: A rationale for careful dissection of individual contributors. Nutrients. (2014). https://www.mdpi.com/2072-6643/6/10/4531
Regulation of energy balance in two models of reversible obesity in the rat. Journal of Comparative and Physiological Psychology. (1979). https://pubmed.ncbi.nlm.nih.gov/521518/
Reprogramming of defended body weight after Roux-En-Y gastric bypass surgery in diet-induced obese mice. Obesity. (2016). https://pubmed.ncbi.nlm.nih.gov/26847390/
Set points, settling points and some alternative models: Theoretical options to understand how genes and environments combine to regulate body adiposity. Disease Models & Mechanisms. (2011). https://journals.biologists.com/dmm/article/4/6/733/3137/Set-points-settling-points-and-some-alternative
The biology of human starvation. American Journal of Public Health and the Nation’s Health. (1951). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1526048/