Learn more about GLP-1 and its role in obesity and diabetes management
Slideshow
Key findings: the Withings GLP-1 study
1,000,000+ connected members whose device data is consistent with GLP-1 treatment, plus a July 2026 survey of 3,716 Withings users.
- Across Withings members on a GLP-1, the median pace of weight loss slowed about 7 times, from 3.8 lb per month in the first four months to 0.55 lb per month after twelve months.
- Across Withings members on a GLP-1, about 24% of the weight lost (about 1 in 4 pounds) was muscle, less than clinical trials report, where general estimates run up to 40%.
- Muscle loss is the #1 concern of Withings users on a GLP-1: 53% name it as a worry (Withings user survey, July 2026, n = 1,620).
- 46.3% of surveyed Withings users on a GLP-1 ranked side effects as the single hardest part of treatment.
- In a randomised trial, people on a GLP-1 drank about 490 ml (17%) less water per day than people on placebo, and Withings members on treatment showed measurably lower hydration.
- In Withings member data, about 40% of flat-scale periods on a GLP-1 were not true plateaus: fat kept leaving while muscle held.
- In trial follow-up, people who stopped a GLP-1 regained about two-thirds of the weight they had lost within a year; among surveyed Withings users who had stopped, 88% said they would consider going back.
- 80% of surveyed Withings users on a GLP-1 said Withings helped their journey, and 95% said tracking their body composition was useful, the highest-rated part of the experience we measured.
Withings members own a connected scale and are not a representative sample of people on GLP-1 treatment. Survey figures are self-reported. Full methodology and references at the end of this page.
What is GLP-1 and how does it regulate your body?
GLP-1 is an incretin hormone naturally secreted by the intestines after eating. As a vital chemical messenger, it performs three primary functions:
Regulates insulin: It prompts the pancreas to release insulin in response to rising blood sugar levels.
Appetite control: It targets receptors in the brain to signal fullness (satiety) and reduce cravings.
Gastric emptying: It slows down the rate at which food leaves your stomach, helping you feel satisfied longer.
A GLP-1 agonist (or GLP-1 analogue) is a medication that mimics this natural hormone but remains active in your system for much longer, providing a therapeutic effect for weight loss and glucose control.
How is a GLP-1 taken, and why does the dose start low?
If you are considering GLP-1 for weight loss, it is vital to understand both the administration and the commitment involved. In the U.S., these FDA-approved medications require a healthcare provider's prescription.
- Administration routes: While weekly subcutaneous injections are standard, oral formulations are also available for certain medications.
- Taking the GLP-1 pill: Unlike injections, the oral version must be taken daily on an empty stomach with no more than 4 ounces of plain water, at least 30 minutes before any food or other medications.
- The titration period: To minimize digestive side effects, doctors typically start with a low dose and gradually increase it over several months.
How does weight loss change month by month on a GLP-1?
In Withings data from 1,000,000+ members, the median pace of weight loss fell from about 3.8 lb per month in the first phase to 0.55 lb per month after twelve months, roughly seven times slower by the end.
Nothing has gone wrong when that happens. A smaller body needs less energy, so the same treatment and the same habits move the scale more slowly over time. Expecting month twelve to feel like month two is the most common way people quit something that is still working.
The four chapters below come from the whole membership, not from any one person. Every journey differs in pace, in side effects and in results. Treat the months as signposts, not a schedule.
| Phase | Months | Median weight loss per month | What people tell us |
|---|---|---|---|
| Starting out: titration and side effects | 0 to 4 | 1.7 kg | “The side effects are worse than I expected.” |
| Finding a rhythm: results arrive, muscle starts to go | 4 to 8 | 1.1 kg | “How do I keep this up for another six months?” |
| When it slows: the plateau | 8 to 12 | 0.6 kg | “Am I doing something wrong?” |
| The landing: long haul, or exit | 12 to 24+ | 0.25 kg | “What happens if I have to stop?” |
Median pace across Withings members whose device data is consistent with GLP-1 treatment. Indicative timing: individual journeys vary widely.
How much weight do people actually lose on a GLP-1?
In the pivotal semaglutide trial (STEP 1), 86% of participants lost at least 5% of their body weight and 51% lost 15% or more at 68 weeks, but about 1 in 7 did not reach 5%.
Three patterns sit inside those numbers. Fast responders lose visibly from the first weeks. Slow responders see very little for two or three months, then start moving. Non-responders, roughly one in seven, do not reach 5% even at full dose. A slow start is not a verdict.
Can you tell in advance which pattern you are likely to follow? Partly. In the Withings study conducted with Mayo Clinic, starting fat mass was the single strongest predictor of how strongly someone responded: the more fat mass at baseline, the larger the response. It is also part of why women in Withings data respond more strongly on average, since they start from a higher fat percentage.
That is why a baseline reading matters. It is not record-keeping. It is the closest thing you have to a realistic expectation.
| Weight lost at 68 weeks | Share of participants |
|---|---|
| 5% or more | 86% |
| 10% or more | 69% |
| 15% or more | 51% |
| 20% or more | 32% |
| Less than 5% | 14% |
Semaglutide 2.4 mg, STEP 1 trial (Wilding et al., New England Journal of Medicine, 2021), reference 1.
How much of the weight lost on a GLP-1 is muscle?
Across Withings members on a GLP-1, about 24% of the weight lost was muscle. Clinical trials report higher shares, some up to 40%. The Withings figure is a median across a large population of people who own a scale and use it; the trial figures come from smaller, closely measured groups. They describe the same reality from two angles.
A quarter of what you lose being muscle is a normal proportion, applied to twice as much weight. Bone mass held steady in Withings data once matched for body size. Hydration is the reading to watch (see below).
Muscle loss is the #1 concern of Withings users on a GLP-1: 53% name it as a worry before they start.¹ They are right to, and not for the reason most people assume. Muscle is your metabolic engine: basal metabolic rate, what you burn simply staying alive, accounts for about two-thirds of daily energy use, and muscle is the tissue that drives it. Lose muscle and the engine gets smaller. The body that has to hold the new weight is a smaller engine than the one that lost it.
That is why protecting muscle while losing is far easier than rebuilding it after. Two things help: strength training two or three times a week, and protein spread across meals rather than one large serving. Ask your prescriber or a dietitian what amount suits you. And if your lean mass is falling, that is a conversation with your prescriber, not a reason to stop.
What are the most common GLP-1 side effects, and when do they ease?
In clinical trials, nausea affected about 44% of people on a GLP-1, diarrhea about 30% and vomiting about 24%. Among surveyed Withings users on a GLP-1, 46.3% ranked side effects as the single hardest part of treatment, ahead of cost, injections and dose management.²
If your first months are rough, that is the majority experience. It is also what the titration schedule is for: you start on a small dose and step up over weeks, precisely so your body can adapt. It feels like a delay. It is the part of the plan doing most to keep you in it. Most side effects are worst in the days after a step up and settle between them. Anything severe belongs with your prescriber, not a forum.
Faced with all of that, almost nobody waits it out passively. Within the first four months, 85.3% of surveyed Withings users on a GLP-1 bought at least one thing to go alongside the prescription, most often supplements and protein foods.³ Nobody coordinates any of it, which is the highest-value thing a prescriber can do for you.
Among Withings users who stopped treatment, 29% named side effects as a reason, second only to cost. Stepping up too fast is one of the few things in this journey within reach, and it is a conversation to have with your prescriber rather than a decision to make alone.⁴
| Side effect | Share of people in clinical trials |
|---|---|
| Nausea | ~44% |
| Diarrhoea | ~30% |
| Vomiting | ~24% |
| Constipation | ~24% |
| Fatigue | ~11% |
Published for specific molecules at specific doses; yours will differ. Reference 1.
Why does dehydration happen on a GLP-1?
In a randomised trial, people on a GLP-1 drank about 490 ml (17%) less water per day and felt less thirsty than those on placebo. Withings members on treatment, matched on sex, age and body size, showed measurably lower hydration than members not on treatment.
Everyone warns you about nausea. Almost nobody warns you about water. It is the risk where three mechanisms stack up at once, quietly, in the phase where you are least likely to notice.
Thirst itself is blunted. These drugs do not only act on appetite. The brain structures that regulate fluid balance carry GLP-1 receptors too, so the signal you would normally trust becomes unreliable.
Food stops bringing water. Between a fifth and a third of anyone's fluid intake arrives through what they eat. Eat substantially less, which is the entire point of the treatment, and that share disappears without a single decision being made about it.
Side effects take more out. Nausea, vomiting and diarrhea remove water on top of the two above. Clinical protocols ask prescribers to monitor hydration during titration.
None of this is cause for alarm. It is cause for a routine. Drink to a schedule, not to thirst: fixed points in the day beat reacting to a sensation the medication has muted. Watch the hydration line on your scale alongside fat and muscle; it is already being measured and it is the one line almost nobody reads. And vomiting or diarrhea lasting more than a day or two is a phone call to your prescriber, particularly with any kidney condition.
What does it mean when the scale stops moving on a GLP-1?
In Withings member data, about 40% of flat-scale periods on a GLP-1 were not true plateaus: fat was still being lost while muscle held or grew. And two in three plateaus were followed by more weight loss, including the long ones.
Weight loss on a GLP-1 was never going to fall in a straight line. The real shape of the journey is loss, pause, loss. Before you change anything, answer one question: how long has it actually been? Clinicians read a flat scale almost entirely by its duration.
A pound of fat out and a pound of muscle in reads as nothing happening on a bathroom scale. Two people can have identical flat months and be in opposite situations. Only one of them needs to change anything, and only body composition tells you which one you are.
One exception is worth acting on quickly: almost no loss at all by month two or three. An early plateau is not simply the dose being low. It is the pattern most likely to respond to an adjustment, and the one most often mistaken for a slow start. Bring it to your prescriber rather than waiting it out.
| How long | What it usually is | The right response |
|---|---|---|
| Under two weeks | A fluctuation, not a plateau. Water, glycogen, digestion and hormones can mask real fat loss for days. | Patience. Read the trend, not this morning's number. |
| Two to eight weeks | A pause. A real stall, but nothing says it is finished. Loss frequently restarts on its own, particularly after a dose step. | Check the basics: habits, protein, sleep, missed doses. Then raise it with your prescriber if it persists. |
| Beyond two months | A durable plateau. Your body has most likely found its new, lighter equilibrium. In obesity medicine this is a normal phase, not a failure. | Specialists treat this as an arrival, not a wall. The goal changes from losing to holding. |
Duration thresholds from obesity medicine practice (reference 10). Plateau frequencies from Withings member data.
“It is very useful to be able to see fairly accurate muscle gain when the actual weight loss stalls. There is power in seeing results of the effort I'm making.”
Withings user, on treatment, 6 months. Verbatim response drawn from a July 2026 Withings user survey of 3,716 respondents.
What else changes in the body on a GLP-1, beyond weight?
Withings members on a GLP-1 showed sustained blood pressure reductions of about 2.5 mmHg systolic and 1.5 mmHg diastolic, alongside a resting heart rate roughly 3 bpm higher than comparable members not on treatment.
Weight is the change everybody watches. It is not the only one, and it is not even the one that changes most predictably. The blood pressure reduction holds rather than rebounds, and falls further with time on treatment. The higher resting heart rate is known for this drug class and worth a mention at an appointment. Overnight breathing disturbances dropped sharply in the first months for the members we could measure, a small sample, so encouraging rather than settled.
All three are readings a connected watch or blood pressure monitor takes at home, in the conditions of daily life rather than a clinic corridor.
| What's changing | What Withings data shows | Direction |
|---|---|---|
| Blood pressure | Sustained reductions of around 2.5 mmHg systolic and 1.5 mmHg diastolic that hold rather than rebound, and fall further with time on treatment. | ↓ Improving |
| Overnight breathing disturbances | Drop sharply after the first months for those we could measure. A small sample, so encouraging rather than settled. | ↓ Improving |
| Resting heart rate | 67 bpm early on, 70 by month twenty-four, against 64 for comparable members not on treatment. Known for this drug class. | ↑ +3 bpm |
What happens if you stop taking a GLP-1?
In trial follow-up, people who came off treatment regained about two-thirds (67%) of the weight they had lost within a year of stopping, usually without a single moment where it became obvious. Among surveyed Withings users who had stopped a GLP-1, cost was the leading reason (33%), and 88% said they would consider going back.⁴
Count what you have already put in. Twelve months. Fifty-odd injections. The nausea weeks. The appointments. That is a serious investment, and far easier to lose than it was to make.
Everything up to here had a direction: down. Maintenance does not. It is the first stretch where “no change” is the goal, and almost nobody arrives at it with any way of telling whether they are succeeding. Losing was the project. Holding it is the job, and it needs a different instrument: fat returning while muscle does not is the pattern to catch early, and a bathroom scale cannot see it.
Three things matter if you are thinking about stopping. Have the conversation before you need to: cost and insurance are the commonest reasons people come off, and both are visible weeks ahead. Keep measuring for at least six months after. And keep strength training, which matters more now than during treatment, and which most people drop.
| What people did after stopping | Share |
|---|---|
| Changed how they eat | 66% |
| Cardio exercise | 52% |
| Strength training | 38% |
| Nothing in particular | 15% |
Withings user survey, July 2026, users who had stopped a GLP-1, n = 152. Regaining weight was the second most common worry across everyone surveyed, yet fewer than four in ten did the one thing that most reliably protects the tissue that keeps weight off.
Does tracking body composition actually help on a GLP-1?
95% of surveyed Withings users on a GLP-1 said tracking their body composition was useful, the highest-rated part of the experience we measured, and 74% said the data kept them motivated.¹
Six months in, the novelty is gone and the routine has to carry you. The strongest thing people told us kept them going was not discipline. It was being able to see something happening, especially on the weeks the scale refused to move.
80% of surveyed Withings users on a GLP-1 said Withings helped their journey.¹ At a plateau, 47% said their data made them more likely to stay on treatment, against 3% more likely to quit.¹ And two in three (65%) share their Withings data with their prescriber.⁵
The honest counter-figure is worth printing: 17% said the data sometimes made things harder.¹ Two people have a legitimate interest in your body composition: you, and whoever prescribed your treatment. They need opposite things from the same measurement. You need to know when to look and when not to. Your prescriber needs the whole line. Measuring is a tool, not a duty: if the numbers stop helping, put them down and mention it at your next appointment.
Five things hold true the whole way through. The trend beats the reading. Muscle is your metabolic engine. A plateau is not a failure. Drink before you are thirsty. And what you keep matters as much as what you lose.
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GLP-1 therapy FAQ
How long does it take to lose weight on a GLP-1?
Loss is fastest in the first months and slows over the first year. In Withings member data, the median pace fell from about 3.8 lb per month early on to about 0.55 lb per month after twelve months. The journey spans roughly twelve months or more before a maintenance phase.
How much of GLP-1 weight loss is muscle?
About 24% in Withings member data, a median across 1,000,000+ members. Clinical trials report higher shares, some up to 40%. Tracking lean mass at home shows whether your own loss is following that pattern.
Is a weight loss plateau on a GLP-1 normal?
Yes. In Withings member data, two in three plateaus were followed by more weight loss, and about 40% of flat-scale periods were fat leaving while muscle held. Read a flat scale by its duration: under two weeks is noise, two to eight weeks a pause, beyond two months a new equilibrium.
Will I regain weight if I stop a GLP-1?
In trial follow-up, people regained about 67% of lost weight within a year of stopping. Keeping muscle is what helps hold a lower weight: strength training and continued measuring for at least six months after stopping are the two habits people most often drop.
What are the most common GLP-1 side effects?
Nausea (about 44% in clinical trials), diarrhea (about 30%) and vomiting (about 24%), usually worst in the days after a dose increase and easing between steps. 46.3% of surveyed Withings users on a GLP-1 ranked side effects as the hardest part of treatment.
Can I get a GLP-1 over the counter in the US?
No. In the United States, GLP-1 medications such as semaglutide or tirzepatide require a prescription from a licensed healthcare professional. Talk to your doctor if you think you may be a candidate.
How we measured
Findings on this page combine two sources. First, passive, continuous device data from 1,000,000+ Withings members whose readings are consistent with GLP-1 treatment: weight, body composition, hydration, blood pressure, heart rate and sleep, collected at home during ordinary life. Second, a July 2026 survey of 3,716 Withings users: 2,409 currently on a GLP-1, 153 who had stopped, and 1,154 who considered it and decided against. Median age 49; 55% of those on treatment were men; 94% US-based.
Comparisons between members on and off treatment are matched on sex, age and body size. Withings members own a connected scale and use it, so they are not a representative sample of everyone on GLP-1 treatment. Survey figures are self-reported and describe choices from fixed options. Journey timing is indicative. The baseline-predictor analysis was conducted with Mayo Clinic (Mayo Clinic Proceedings: Digital Health, 2026).
¹Withings user survey, July 2026, n = 1,620.
²n = 3,716.
³n = 523.
⁴n = 152.
⁵n = 582.
Devices: Withings body composition scales, ScanWatch, BPM Vision.
References
1. Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med. 2021;384(11):989-1002.
2. Wilding JPH, Batterham RL, Davies MJ, et al. Weight regain and cardiometabolic effects after withdrawal of once-weekly semaglutide. Diabetes Obes Metab. 2022;24(8):1553-1564.
3. Kennedy C, Hayes P, Salman S, et al. The effect of semaglutide on blood pressure: a systematic review and meta-analysis. Diabetes Obes Metab. 2023.
4. Nauck MA, Quast DR. Cardiovascular safety and benefits of semaglutide: heart rate effects. Front Endocrinol. 2021;12:645566.
5. Cava E, Yeat NC, Mittendorfer B. Preserving healthy muscle during weight loss. Adv Nutr. 2017;8(3):511-519.
6. Withings. Body composition change during GLP-1 treatment. Mayo Clinic Proceedings: Digital Health. 2026.
7. Randomised controlled trial of dulaglutide reporting reduced fluid intake (~490 ml/day) and lower thirst perception vs placebo.
8. GLP-1 receptor expression in the organum vasculosum and subfornical organ of the lamina terminalis; reduced water intake independent of food intake in animal models.
9. Case report: acute kidney injury secondary to dehydration following persistent semaglutide-associated vomiting.
10. Weight-loss plateau: duration thresholds and metabolic adaptation in obesity medicine practice.
11. Withings internal analysis: GLP-1 user survey linked to connected-device measurements, July 2026, n = 3,716.