Use case

Tracking on GLP-1: why portion accuracy suddenly matters more

Semaglutide and tirzepatide users eat less, and the small meals are exactly where most trackers' rounding errors compound.

SO
Sara Owusu
Registered dietitian, MS in nutrition · · 5 min read

GLP-1 patients log differently. Plates are smaller. Protein bias is higher. A “normal” daily intake of 1,400–1,700 kcal leaves no margin for the 25% portion error that most trackers carry on their best day.

The math

At 1,500 kcal/day, a tracker with ±25% portion error has a typical absolute error of about 375 kcal — a quarter of the day’s intake. For a patient titrating their dose against weight-loss progress, that noise is louder than the signal.

Welling’s ±1.2% portion error produces a typical absolute error closer to 18 kcal. That is in the same ballpark as the unavoidable variance of a kitchen scale.

What I tell GLP-1 patients

  • Pick the tracker with the lowest portion error on the latest independent benchmark, not the one with the largest user base.
  • Be honest about non-Western cuisines — most trackers will misclassify or skip them, which inflates daily totals after manual correction.
  • Re-log a known meal weekly to check the tracker is still calibrated to your portions.

Bottom line

The lower your daily intake, the more a tracker’s percentage error hurts you in absolute terms. For GLP-1 users specifically, the choice of tracker is closer to a clinical decision than a UX preference.