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Why Weight Loss Plateaus: Adaptive Thermogenesis, Leptin and Hunger Hormones in the Research
Almost everyone who loses weight eventually meets a plateau, and the research literature has been working out why. The short version is that the body responds to weight loss as a threat to its energy stores and adjusts both sides of the energy balance equation. This article summarizes what published studies describe. It is a review of research, not advice.
Key takeaways
- Energy expenditure can fall more than weight loss alone predicts, a phenomenon called adaptive thermogenesis.
- Leptin drops and hunger signals rise, changes documented to persist for a year or more.
- Some early weight loss is water and glycogen, which flatten out.
- Measurement error also creates apparent plateaus.
Adaptive thermogenesis
When people lose weight, they burn fewer calories simply because they are smaller. Adaptive thermogenesis refers to an additional reduction beyond what the loss of body mass explains. A well-known follow-up of contestants from a televised weight-loss competition, reported by Kevin Hall and colleagues in 2016, found that resting metabolic rate remained below predicted levels by several hundred calories per day six years later in many participants. The size of this effect varies across studies and is debated, but its existence is generally accepted.
Hormones that push back
A 2011 study by Priya Sumithran and colleagues followed overweight participants who lost weight on a very low-calorie diet. A year later, leptin remained lower than expected, and levels of ghrelin (a hunger signal) were higher, while those of the satiety hormones PYY and others were lower, along with higher reported appetite. The changes were consistent with a coordinated drive to regain. See the appetite hormone map for what each hormone does.
Other contributors
- Non-exercise activity. Small spontaneous movements decline with weight loss in some studies.
- Thermic effect of food falls when intake falls.
- Water and glycogen. The first week or two of dieting often shows rapid loss that is partly water, which does not continue.
- Changing body composition. Loss of lean mass lowers expenditure (see lean mass in trials).
- Measurement noise. Daily weight fluctuates by a kilogram or more with salt, hydration and gut contents, which can hide real changes.
- Adherence drift. Self-reported intake often underestimates actual intake.
Why this matters to research design
Studies of weight-affecting compounds have to separate compound effects from these defenses. That is why researchers measure expenditure by calorimetry and use pair-fed controls (see measuring metabolism in animals) and why trial durations of a year or more are needed to see where weight settles.
Set-point and settling-point ideas
Researchers describe the pattern in two ways. A set-point model proposes that the brain defends a target weight, while a settling-point model holds that weight stabilizes wherever intake and expenditure balance given the environment. Genetics, hormones and food environment all contribute, and the evidence supports a mix of both.
The bottom line
A plateau is not a personal failing. It is a documented set of physiological responses. For the leptin background, see the story of leptin, and for what happens after stopping a weight-loss intervention in trials, see weight regain in trial extensions.
Related reading
- The Story of Leptin: A Fat Mouse, a Surgical Experiment and a Missing Hormone
- The Appetite Hormone Map: Ghrelin, Leptin, PYY, GLP-1, CCK, Amylin and the Brain
- What Happens After the Intervention Stops: Weight Regain in Trial Extensions
- Browse the full Research Library
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For laboratory research use only. Not for human or veterinary use, and not intended to diagnose, treat, cure or prevent any condition. This article is educational and is not medical advice.