Set point weight theory claims that a person’s body aims to maintain fat mass and weight at a predetermined range. It may explain why people tend to regain the weight they lost while dieting.

This return of lost weight following a decrease in weight loss efforts is very common. According to research, it happens more than 80% of the time.

One explanation for this involves the interactions between parts of the brain that control feeding and hormones that control satiety, or a feeling of fullness. Other research argues against set point theory, claiming that environmental, economic, and societal factors may play a role.

Keep reading to learn more about set point weight theory, including arguments for and against it, whether a person can change it, and what it means for weight loss.

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Set point theory is the idea that every person’s body has a predetermined fat mass or weight range.

It claims that when a person eats less than their usual amount — resulting in weight loss — various physiological mechanisms come into play. These mechanisms drive the weight back to the set point, which results in regaining the lost weight.

The theory also includes the reverse situation. This means that when someone eats more than their usual amount — resulting in weight gain — mechanisms drive the weight back to the set point, which results in a loss of the gained weight.

In other words, the theory relates to homeostasis, where body processes work to maintain a stable weight equilibrium.

However, mechanisms that reverse weight gain are weaker than those that reverse weight loss. This means that set point theory is more applicable to regaining lost weight than the opposite.

Factors that maintain a person’s set point

Proponents of set point theory contend that some factors include neurohormonal changes and adaptive thermodynamics.

Neurohormonal changes refer to interactions between feeding centers in the brain and hormones that regulate satiety. This means that when a person loses weight, the body increases levels of hormones that boost appetite and decreases levels of hormones that suppress appetite.

Adaptive thermodynamics means that when an individual does not consume enough calories, their body makes adaptive changes that decrease resting energy expenditure.

It is worth noting that the set point theory is unproven. Some researchers consider it oversimplistic.

A 2018 study presents the below arguments for and against it:

Arguments for

Evidence supporting set point theory comes mostly from animal studies. Researchers found that after feeding animals a diet that promotes weight gain or weight loss, discontinuing the diet results in a return to the pre-diet weight.

Research on humans has used data from large groups of people who have gone through weight loss programs. Results showed that after losing some weight, most people regained it, returning to a weight similar to their previous weight.

Arguments against

There have been very few clinical trials on set point theory. Most research comes from observational studies, and it is impossible to control variables in these situations.

For these reasons, human studies do not support the theory.

Indirect evidence of alternative factors to set point theory comes from data showing there is a twofold increase in obesity today compared with obesity in the previous generation. This suggests that instead of a biological set point determining weight, the following factors may underlie it:

  • Environmental: This includes modern-day lifestyle factors, such as the availability of fast-food outlets and high calorie snacks.
  • Economic: A lower income may limit access to healthy food — such as fruits and vegetables — which are naturally lower in calories.
  • Societal: Communities with poorer socioeconomic characteristics may have a food environment that is less healthy. For example, people may live in food deserts.

There is very little a person can do to change their set point weight. Some experts believe that bariatric surgeries, which can help with long-term weight loss, may alter a person’s set point weight.

Two surgeries that may change the set point are vertical sleeve gastrectomy (VSG) and roux-en-Y gastric bypass (RYGB). VSG removes most of the stomach, and RYGB creates a pathway for food to go from the food pipe to the intestine, bypassing the stomach.

These surgeries produce more long-term weight sustainability than lifestyle changes alone.

However, bariatric surgery can have negative effects, such as harming the bacterial community in the gut, which affects nutrient extraction from food. It may also cause other side effects, some of which are serious, so they are not a safe option for everyone.

Understanding set point theory may help scientists discover the underlying causes of obesity.

Finding the mechanisms responsible for the set point may lead to safe and less invasive treatment options. It may also bring to light measures that may prevent obesity.

Additionally, the knowledge that a weight set point exists may reduce the stigma associated with obesity.

The fact that most people who lose weight while on a diet later regain it may support the set point weight theory. This is a belief that physiological mechanisms aim to keep weight and fat at a fixed range.

While some animal studies indicate that a set point may exist, other research suggests that regaining lost weight after dieting may stem from environmental, economic, and societal factors.

Some types of bariatric surgery may change the set point, but these procedures have side effects and are not safe for everyone.