Why Weight Loss Plateaus on Semaglutide or Tirzepatide — and What to Do About It
- Joshua Silva, MD
- 5 days ago
- 6 min read
Updated: 2 days ago
Many people taking semaglutide or tirzepatide notice that weight loss is faster at first and then slows or pauses over time. This plateau can be frustrating — but it is expected, well-documented in clinical trials, and driven by normal human physiology, not a failure of the medication or the patient.
This article explains why plateaus happen, what the research shows, and what evidence-based options exist when weight loss slows.
Weight Loss Plateaus Are Normal — and Seen in Every Major GLP-1/GIP Study
The Standard Weight-Loss Curve
Clinical trials consistently show that weight loss with GLP-1 and GLP-1/GIP medications follows a predictable pattern:
Rapid weight loss early
Gradual slowing over time
A plateau phase where weight stabilizes
This pattern has been observed across:
Semaglutide trials (STEP program)
Tirzepatide trials (SURMOUNT-1, SURMOUNT-4)
Long-term cardiovascular outcomes studies (SELECT)
In these studies, most participants lost weight more rapidly during the first several months, then experienced a gradual slowing and reached their average maximum weight loss around 9–18 months, after which weight tended to stabilize rather than continue to drop indefinitely.
This plateau reflects the body reaching a new steady weight, not that the medication “stopped working.”
Why Plateaus Happen — The Metabolic Explanation
A Smaller Body Needs Fewer Calories
As weight decreases, your body naturally burns fewer calories at rest and during daily activity. This is true regardless of how the weight was lost — through medication, diet, surgery, or lifestyle changes.
Simply put:
A 220-lb body requires more energy than a 180-lb body.
As weight drops, daily calorie needs fall.
So the same eating pattern that produced weight loss early does not cause indefinite weight loss — but it does help maintain the new, lower weight once a plateau is reached.
Metabolic Adaptation (“Adaptive Thermogenesis”)
Beyond body size alone, the body also responds to weight loss by becoming more energy-efficient — a phenomenon called adaptive thermogenesis.
This includes:
A drop in resting metabolic rate beyond what the new body size predicts (see table below)
Increased biological signals that encourage eating and decreased leptin.
Reduced spontaneous movement (NEAT – Non-Exercise Activity Thermogensis; beyond the scope of this post but an fascinating phenomenon)
Importantly, GLP-1 and GLP-1/GIP medications do not fully eliminate this response. Clinical studies show that metabolic adaptation still occurs during weight loss with semaglutide and tirzepatide — which helps explain why plateaus are common even with effective medication.
Effects of 10% Reduction in Weight | |
24 hr energy expenditure | Decreased 15% |
Non-resting energy expenditure (NEAT) | Decreased 30% |
Skeletal muscle work efficiency (muscles burn less calories to do the same amount of work) | Increased 20% |
Notes: | A 10% decrease in weight produces more than a 10% decrease in basal metabolism. |
Table adapted from: Müller MJ, Bosy-Westphal A. Adaptive thermogenesis with weight loss in humans. Obesity (Silver Spring). 2013;21(2):218–228.
Calories In vs. Calories Out Still Matters
The Energy Deficit Shrinks Over Time
Weight loss requires a calorie deficit — burning more energy than is consumed. GLP-1/GIP medications help by:
Reducing appetite
Increasing fullness
Decreasing food cravings
However, studies have demonstrated that over time:
Appetite suppression may soften slightly
Portion sizes may slowly increase
Energy needs fall as body weight decreases
When calorie intake and calorie expenditure find a new equilibrium, weight loss slows or stops — creating a plateau.
This process is physiological, not behavioral failure. Importantly, the medication is still doing its job if weight is being maintained at a lower, healthier level.
Are Your Results Still “Normal”? Setting Realistic Expectations
Many patients worry that they have plateaued too early or are not getting the full benefit of semaglutide or tirzepatide. To put this in context, it helps to look at what clinical trials show as typical, expected weight loss with these medications.
What Clinical Trials Show
In large obesity trials:
Average weight loss is ~15% of starting body weight with semaglutide 2.4 mg
Average weight loss is ~20–22% of starting body weight with tirzepatide 15 mg
The majority of weight loss occurs within the first year of treatment
Plateaus are common after significant weight reduction
Some people lose more, some less — but a flattening of the weight-loss curve is expected, especially after meaningful progress has already occurred.
If you have lost approximately 15–21% of your starting weight and are now plateauing, your response is very consistent with clinical trial outcomes.
What a Plateau Does Not Mean
A plateau does not mean:
You are resistant to the medication
The dose has stopped working
Weight regain is inevitable
Reaching a plateau after substantial weight loss is a sign of physiologic adaptation — not treatment failure.
Evidence-Based Options When Weight Loss Plateaus
When weight has been stable for several weeks despite adherence, there are three scientifically supported paths forward:
Adjust Calorie Intake
Because calorie needs are lower at a reduced weight, you may need to decrease total calorie intake even further. Focus on modest dietary adjustments — not extreme restriction — to re-establish a sustainable deficit.
Increase Energy Expenditure
Increasing activity helps counter metabolic slowing and burns more calories. Evidence supports even simple activities like:
Higher daily step counts
Resistance training to preserve lean mass
Maintaining muscle to support metabolic health (muscle burns more resting calories)
Optimize Medication Dose
Maximum average weight loss in GLP-1/GIP clinical trials occurred at higher doses. If you are not yet at a maximally tolerated, effective dose, gradual dose escalation under medical supervision may improve appetite control and support further weight loss.
Has Enough Time Passed? Why Patience Matters
In the pivotal obesity trials, total weight loss with semaglutide and tirzepatide was assessed over about 68–72 weeks (roughly 16–18 months). Weight loss is typically fastest in the first 3–6 months, then slows but may continue gradually before plateauing around ~12 months or later. During this later phase, ongoing loss may average about 1–2 lb per month, which can feel slow but adds up over time.
If you are still within the first year of treatment, this pattern often reflects normal progression rather than a true plateau.
The Bigger Picture — Plateaus Are Part of Long-Term Success
A weight-loss plateau often signals a transition from rapid loss to long-term maintenance. At this stage, many patients continue to see improvements in:
Blood sugar control
Blood pressure
Lipids
Inflammation markers which lower cardiovascular risk
Mobility and quality of life
Focusing only on the scale can miss these meaningful health gains.
Key Takeaway
Weight loss plateaus on semaglutide or tirzepatide are expected, evidence-based, and driven by normal metabolic physiology. They occur because:
A smaller body needs fewer calories
Metabolism adapts to defend weight
The initial calorie deficit narrows over time
With appropriate adjustments — dietary, activity-based, or medication-related — many patients can continue progress or successfully maintain their healthier weight.
Disclaimer:
This article is for educational purposes only and is not a substitute for medical advice.
About the Author
Dr. Joshua Silva, MD, is a licensed physician and Medical Director of Potere Health MD. After graduating medical school from the University of Hawaii, he completed residency training in Occupational and Environmental Medicine from the University of Utah where he also earned a master's degree in Occupation Health. He now specializes in evidence-based weight management, including GLP-1/GIP therapies (semaglutide & tirzepatide). Dr. Silva provides in-person and virtual care for patients with clinics in Salt Lake City, St. George, and Cedar City, Utah.
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