Written by Frances Molé
Set Point Theory
Set point theory states that the human body has a preferred natural weight range that the body it will fall within throughout adult life, if there is no impact of dieting or illness. This weight range is predetermined by various factors to maintain balance and function properly (1). If you go above or below the set point range your body will compensate by changing metabolic rate, hunger signals and altering essential functions such as heart rate and body temperature.
What is the set point range?
The term set point implies that there is one point at which your weight is set; however, your set point happens to be a range. Research indicates that your set point will regulate an average range of 5-10 kg (2). This range is the weight your body was designed to be in homeostasis or balance.
What factors influence set point range?
The complex factors used in the body to maintain weight are based on the food we eat and the metabolic response to our diet, which is influenced by hormonal, genetic and environmental factors such as the western diet or a busy lifestyle (1). According to this theory, body weight regulation is adjusted by food intake or energy expenditure (or both) in proportion to the difference between the current body weight and the set point weight (3).
With set point theory, your metabolism will slow if you start eating fewer calories, a process called metabolic adaptation (more on this later). Our nutrient absorption is altered, and hormones change, making you feel hungrier and preoccupied with the thought of food (4). This preoccupation with food occurs when hormones trigger your brain and carries the message of whether to eat more or not and may persist with continuous food restriction.
For example, when we are unwell, our body will adjust to conserve energy by lowering our temperature and increasing our appetite (5). Conversely, when we are on holiday and eat more than usual, our appetite decreases, and body temperature increases to assist in energy unilisation. These changes, along with other physiological systems, are due to evolutionary traits to protect the body and keep it within balance.
Can my set point change over time?
As mentioned, there is a body weight range that is genetically predetermined however, it is possible to make dramatic, short-term changes to weight by manipulating our food intake, but the evidence suggests that these changes are difficult to sustain long term as the body is is driven to return to a healthy weight (if this is different to the weight change achieved). Diets predict weight gain (not weight loss) over a period of two years (6). Initially, weight loss may be rapid however after about 6 months this rate slowly declines until weight stabilises itself or regains to its predetermined, set point (6).
This short-term weight loss, followed by weight regain is what may be termed as the Nike Swoosh Effect (7). Those who weight cycle or go on yo-yo diets can repeatedly undergo initial rapid weight loss followed by weight re-gain and go through this cycle again and again (8). Over time, if you plot your continuous attempts or weight cycles on a graph it may look something like the Nike swoosh (7,8).
Your set point is not tightly controlled but a 'loose' range involving upper and lower limits in weight. After a period of overeating, undereating, and re-feeding after starvation, your set point may have a considerable change (9). It has been shown that re-feeding will increase body weight (see overshoot theory in eating disorder recovery), but after some time, when the body is safe and healthy again, it will regulate itself within 5% of the set point range (10,11). This means that your body weight will vary between different weights that are within a set point range after returning to your pre-starvation weight.
For example, if your set point is around 65kg, this weight may drop significantly after a period of starvation. After re-feeding or overfeeding, your body weight will "overshoot" or increase above 65kg before your body stabilises within a set point of 5% (e.g. ~68kg). Keep in mind this is just an example and may look different for everyone.
Set point theory may explain how weight is typically stable over a long period when not impacted by dieting or illness. However, this theory may be criticised as it doesn't explain the environment's significant impact on our biological body weight control systems (3). For example, lifestyle changes can impact changes in body weight overtime like for those with limited access to healthy foods, socioeconomic influences, and lifestyle changes (i.e., becoming less active as we age, busy and stressful work, etc).
Can my metabolism be ruined through restrictive dieting?
A question that is frequently asked is whether metabolism can be ruined after periods of unbalanced eating (i.e., undereating, overeating, and re-feeding). The answer is that metabolism can't be 'ruined' or 'damaged'; as this suggests that metabolic changes are irreversible. When actually, the natural body process is undergoing metabolic adaptation. This metabolic adaptation is how our body responds and adjusts our metabolism to what we eat (10,11).
Remember that metabolism is the array of chemical processes that occur in our body, metabolic rate is the energy required to fuel these processes.
Due to the dynamic nature of metabolism, multiple components of how our bodies metabolise energy from the food we eat will be affected when food is restricted and weight drops below what is healthy for us. One main component of metabolic rate is the Basal Metabolic Rate (BMR), which refers to the energy your body uses to function at rest. When you lose weight, your body adjusts this BMR by slowing down to prevent starvation, diminish energy balances, and promote long-term weight stability (12, 3). So, rather than the metabolism being ruined, it is adjusting accordingly to the energy we have available and prioritising its highest needs first, like organ function.
Understanding your set point and body diversity
As mentioned, many factors contribute to your set point or natural weight and how it may change over time. If you feel that your natural weight is not where you’d life it to be, it is essential to remind yourself that body acceptance is key and that your body shape or weight might change during the recovery process. Your weight is genetically predetermined and unlikely to change within it’s set point range (if there is no attempt to change it or other medical reasons), so embracing your uniqueness is necessary for recovery. Set point will vary from person to person, like height, hair, and eye colour.
To gain a deeper understanding of body diversity, let's highlight a few points:
As discussed earlier, there can be ranges for set point involving upper and lower limits like ranges in Body Mass Index (BMI). BMI is a population measure for a wide range of body shapes that may exist, it is used as a tool at the population level rather than an individual assessment (13). BMI doesn’t consider body mass, bone index, sex differences and ethnicity. Learn more on The Truth About BMI
People of all weights, shapes, and sizes can experience various medical conditions, including eating disorders. You cannot accurately assess a person's health status by appearance alone.
Weight loss at any size and body shape can be a health risk indicating malnutrition.
You can change your feelings about your body and its uniqueness without losing weight. This can be done by transforming thoughts and beliefs and changing behaviours, life comparison, and self–criticism.
Eating a well-balanced diet and engaging in joyful exercise will assist your body in staying at a healthy, natural weight range, keep you from being preoccupied with food and hunger, and allow your body to function as it should.
In conclusion, with some final throughs on set point theory, the body has a predetermined set point weight that may be in a range of 5-10kg throughout the lifespan. Various changes in the body will occur when the body is above or below this number and it feels threatened by starvation or overnutrition. Continuous manipulation of your body or yoyo diets may cause your set point to change over time. Maintaining habits to maintain the set point that is natural for you and accepting where your body weight settles naturally is necessary for recovery.
Taking the first step towards eating disorder recovery can feel huge and daunting. We get it. If you would benefit from specialist support through your recovery journey we invite you to book a free 15 minute discovery call with one of our eating disorder dietitians at the TC Nutrition Clinic to discuss how we can support you.
Frances is a student dietitian at Bond University, in Australia. She is upskilling in the area of eating disorders and enjoys recipe development and food photography. Her food philosophy is to always include favourite foods, a few simple changes can have the biggest impact on your health. You can find Frances on Instagram @wellnutritionn
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