What happens when you stop a weight-loss injection

Almost everybody asks this question eventually, and most ask it late. The honest answer is that what happens when you stop was largely decided by what you did while you were on it.

The trial data, plainly

The extension study attached to STEP 1 followed participants for a year after both the drug and the lifestyle support were withdrawn. They had lost 17.3 percent of bodyweight. They regained 11.6 percentage points of it, leaving 5.6 percent still off. Roughly two thirds of the loss came back. Cardiometabolic improvements reverted towards baseline for most variables along with it.

That result surprises people who understood the drug as a course of treatment with an end date. It surprises nobody who has watched appetite return to a body that has spent a year learning to be smaller.

Why the weight comes back

Two forces, and they push in the same direction.

The first is appetite. These drugs work by suppressing it. Remove the drug and the suppression goes with it, and what returns is not the old appetite but the appetite of a body that has been in deficit, which is a stronger thing.

That is not a figure of speech. Sustained energy restriction shifts the hormones that govern hunger and does not shift them back on any convenient schedule. Ghrelin, which drives hunger, rises. Leptin, which signals sufficiency, falls. The adjustment is an adaptive response to weight loss and it exists specifically to promote regain, which it does rather well.

So the person coming off the drug is not returning to their old appetite. They are meeting a new one, built during the year they were losing, and meeting it without the thing that was holding it down.

The second is the part this section keeps returning to. A body that lost lean tissue on the way down spends less energy at rest than the same bodyweight with more muscle on it. The person who arrived at 78 kg having lost 4 kg of lean tissue is defending that weight with a smaller engine than the person who lost 1 kg of it.

Tissue is not the whole of it, in fairness. Resting expenditure also falls by more than the lost tissue alone accounts for, a separate adaptation that shows up reliably after weight loss and appears to persist past the point the weight stops moving. How long it lasts and how large it is are still argued over, so I will not put a number on it. So the muscle is one lever among two, and it happens to be the only one you can pull.

Put the two together and the arithmetic of maintenance becomes clear. A smaller person, with less muscle than they could have had, defending a new weight against a hunger drive stronger than the one they started with, on a metabolism running below what their new size would predict. Nobody is failing at maintenance for lack of character.

Same number on the scale. Different job to hold it.

What this changes about the year you are in now

If regain risk is set partly by body composition, then the work that matters is not scheduled for the end. It is happening right now, in whether protein is being eaten and whether muscle is being loaded.

The numbers on both of those are not encouraging. In a study of sixty people on these drugs, 10 percent reached a protein intake of 1.6 g per kg per day, and only 53 percent reported training more than they had before. Which means the majority are building the composition they will have to defend with, without either of the two things that would improve it.

Both halves have their own page: why the protein target is so rarely reached, and what the lean tissue loss actually amounts to.

People tend to treat the drug phase as the easy part and the maintenance phase as the hard part that comes later. That is backwards. The phase you are in is where the defensibility of the result gets built or lost, and by the time you are off the drug the composition of the body you are defending with is already decided.

Questions worth asking your doctor before you stop

These are medical decisions and not mine. But the private clients who came off badly were mostly the ones who never asked:

• Is coming off the plan at all, or is this a long-term medication for a long-term condition?
• If stopping, over what period, and tapering or not?
• What is being monitored on the way down, and how often?

I do not prescribe, adjust or stop these drugs, and I would be suspicious of any nutritionist who offered to. What I can do is make sure the body arriving at that conversation is in a state to handle the answer.

The uncomfortable version

Some people will need to be on something long term. Obesity behaves like a chronic condition with a set point that defends itself, and treating a chronic condition with a temporary intervention has never worked well in any other field of medicine.

That is not a failure of willpower and it is not a reason to avoid the drug. It is a reason to stop thinking of the months you are in as a sprint with a finish line, and to use them to build something that survives the stopping.