Why has my weight loss stopped? The biology of a plateau, and what to do next

Somewhere around the sixth month, the line on the graph goes flat. The same habits that moved it for months stop moving it, and the search begins for what went wrong.

Usually, nothing. The flat line is the expected shape, and it has a mechanism.

Is it normal for weight loss to stop?

Yes: a 2007 review pooled eighty trials of diet, medication or both, and the curve looked the same almost everywhere: steepest in the first six months, then levelling off. Four years on, people in those trials were still about three to six kilograms below where they started on average, and no pooled result had returned to baseline.

Medication moves the curve but keeps its shape. The SELECT trial followed about seventeen and a half thousand adults with cardiovascular disease and overweight or obesity but no diabetes. On semaglutide, their weight kept falling until about fifteen months. After that it held, still about ten per cent lower at four years against one and a half per cent on placebo.

What is your body doing when the scale stops?

Your treatment pulls weight down, and as it comes off, your body pulls back, mostly through appetite. One analysis, using energy intake calculated from a model in people with type 2 diabetes, put that push at about a hundred calories a day for every kilogram lost. That is more than three times the drop in what the body burns.

Weight settles where the new intake meets the new expenditure, and it approaches that point slowly. A 2011 model in The Lancet puts the halfway mark at about a year. Picture a tug-of-war in which the other team gains a player for every metre you win: the rope stops moving when both sides pull equally, not when either side lets go. We covered the defence itself in why your body fights weight loss.

Is my metabolism broken?

No. It slows, but modestly: in 171 women with overweight, measured once their weight was stable, the fall at rest was about fifty calories a day, and it did not predict who regained.

At the extreme the slowing was larger and lasting: six years after a televised weight-loss contest, where fourteen people lost about fifty-eight kilograms in thirty weeks, it was still about five hundred calories a day. Yet the slowing at the end of the contest did not predict who regained. The largest slowing six years on was in those who had kept the most weight off. The authors called it a proportional, but incomplete, response. Appetite does more of the work.

Is it a plateau, or is it water?

Often, water. Stored carbohydrate holds three to four times its weight in water, so a heavier-carbohydrate day can nudge the scale up the next morning without any change in fat. In a Finnish study of eighty adults who weighed themselves often, weight ran highest on Sunday and Monday and drifted down through the week. Many women also notice fluid shifts across the menstrual cycle.

So a plateau is a flat trend over several weeks, and one disappointing morning can't show it.

Has my medication stopped working?

Usually not. A steady weight on medication is often the medication holding a lower weight against that rising appetite. In the STEP 4 trial, people who continued semaglutide after twenty weeks lost a further eight per cent or so of their weight. Those switched to placebo regained about seven per cent.

The 2022 pharmacotherapy chapter of the Canadian guideline suggests a review when goals aren't met: the dose, what makes treatment hard to keep up, barriers to changing habits, and other medical or psychosocial issues. It suggests considering another medication or approach after three to six months on the highest dose a person tolerates. The 2025 update notes that treatment goals may be reached at a dose lower than the maximum. Cost is a fair thing to raise with your prescriber too.

A plateau is a review, not a restart

Modelling work has shown that a six-month plateau appears even when people follow their plan closely. So the useful question isn't whether you tried hard enough. It's what has changed around you, in sleep, stress, medications or appetite, and what the numbers besides weight are doing. Small drifts happen to everyone, and a rising appetite is the body working as designed. The 2022 chapter notes that health can improve substantially even without five per cent weight loss.

• Look past the scale. Waist, blood pressure, blood sugar, liver tests, sleep and strength can keep improving at a steady weight. Our body composition article explains why.
• Protect muscle. Protein and resistance work, at whatever level your body allows, help protect muscle, as we covered in losing weight without losing strength.
• Check the other levers. Sleep, stress, new medications and pain are worth reviewing too.

How we approach this at GOALS

GOALS is the obesity and lifestyle medicine program at Guelph Internal Medicine Clinic, and the medical care is covered by OHIP, by referral from your family doctor or nurse practitioner. We treat obesity the way medicine treats any other chronic condition, and we track progress with objective measurement, not the scale alone.

This week, put a tape measure beside the scale. A waist still coming down under a flat line is the rope holding, and that ground is yours.