Why has my weight loss stalled on a GLP-1?
Most weight loss plateaus on a GLP-1 are not plateaus at all — they are normal fluctuation, or a dose that has not yet reached therapeutic level. A real plateau is four weeks or more with no downward trend, measured fortnightly at the same time of day. When it is real, the commonest causes are protein intake that has quietly fallen too low, liquid calories, and the absence of resistance training. A genuine physiological plateau, where your body has adapted to a lower weight, normally arrives around month nine to twelve and not before.
First, check whether it is actually a plateau
Most reported plateaus are not real. Body weight swings by one to two kilograms across a normal week from fluid alone, and more than that around illness, salt, carbohydrate intake, hard training or the menstrual cycle.
The working definition worth using is four weeks or more with no downward trend, weighed fortnightly, same time of day, same clothing, ideally first thing. If you are weighing daily and reacting to it, you are reading noise and it will drive you mad.
One more check before you change anything: are your clothes fitting differently? Body composition can shift meaningfully while the scale sits still, particularly if you have recently started resistance training. That is a good outcome wearing the disguise of a bad one.
Cause one: you are not at a therapeutic dose yet
By a distance the commonest explanation, and the easiest to mistake for failure.
On Wegovy you do not reach 2.4 mg until week 17. On Ozempic, 0.25 mg for the first four weeks is a starting dose that was never expected to shift weight. On Mounjaro, 2.5 mg is the same. If you are inside the titration and the scale is flat, the treatment is not stalling. It has not started.
Cause two: protein has quietly fallen too low
This is the one that catches careful people. GLP-1 treatment suppresses appetite indiscriminately, and protein is the macronutrient people drop first because it is the most filling and the least appealing when you are already not hungry.
The target most clinicians work to is roughly 1.2 to 1.6 g of protein per kilogram of body weight per day. At 90 kg that is 108 to 144 g, which is a genuine effort when a small bowl of soup feels like a full meal. When protein falls short, lean mass goes, resting metabolic rate follows it down, and the scale stops moving. Track it honestly for three days before concluding anything else.
Cause three: liquid calories
GLP-1 medicines work partly by slowing gastric emptying and increasing satiety from solid food. Liquids largely bypass that mechanism.
Alcohol is the biggest offender, and the most common invisible reason for a flat month. Three pints is roughly 600 kcal that produced no fullness at all, plus the appetite disinhibition that follows. Coffee shop drinks, smoothies and fruit juice work the same way on a smaller scale. None of this requires abstinence, but it does require counting.
Cause four: no resistance training
Without resistance training, a substantial share of what you lose on a GLP-1 is muscle rather than fat. Estimates across the literature run from about a quarter of total weight lost to well over a third at higher doses.
Muscle is metabolically active. Lose enough of it and your resting energy expenditure falls far enough to cancel out the deficit the medication created. Two or three sessions a week is enough to change this substantially, and it does not need to be a gym.
Cause five: a genuine physiological plateau
Real, and expected, but usually later than people assume. As you lose weight your body needs fewer calories simply because there is less of it to move and maintain, and adaptive thermogenesis lowers energy expenditure further.
On the trial curves, this typically appears around month nine to twelve. In SURMOUNT-1 the average curve flattened toward week 72. If you are four months in, this is almost certainly not what is happening to you.
Cause six: genuine low response
A minority of people respond poorly to semaglutide or tirzepatide despite an adequate dose and everything else being right. It is recognised in the literature, it is not a matter of effort, and it is not common.
It is also worth ruling out other explanations before landing here: untreated hypothyroidism, some antidepressants and antipsychotics, corticosteroids, and sleep apnoea all blunt weight loss and all are checkable.
When to speak to your prescriber
Four weeks flat at a full dose, with protein and training accounted for, is the point to raise it. The usual options are a dose increase where headroom remains, a check for another cause, or a switch. People who respond poorly to semaglutide sometimes respond well to tirzepatide, because it acts on a second receptor.
What not to do: increase your own dose, add an extra injection, or buy pens from an unlicensed seller. The HPRA has warned repeatedly about falsified GLP-1 pens reaching Irish patients, and dose errors produce severe vomiting and dehydration rather than faster results.
Weight loss plateau: common questions
Anything under four weeks is usually normal fluctuation rather than a plateau. A genuine stall is four weeks or more with no downward trend when weighed fortnightly at the same time of day.
The commonest reasons are not yet being at a therapeutic dose, protein intake that has fallen too low, liquid calories, and no resistance training. A true physiological plateau normally arrives around month nine to twelve rather than early on.
That is a decision for your prescriber. There is often headroom in the titration, but increasing your own dose or adding an extra injection raises the risk of severe vomiting and dehydration without producing faster weight loss.
Roughly 1.2 to 1.6 grams per kilogram of body weight per day. At 90 kg that is about 108 to 144 grams. Appetite suppression makes this genuinely difficult, and falling short is one of the most common causes of a stall.
Alcohol largely bypasses the satiety mechanism these medicines work through, so it adds calories without producing fullness, and it tends to disinhibit appetite afterwards. It is one of the most common invisible reasons for a flat month.
Usually yes, if the cause is addressable. Correcting protein intake, adding resistance training, removing liquid calories or completing the dose titration all restart progress for most people. A genuine physiological plateau is harder and is a conversation with your prescriber.