In one sentence
How far your glucose fell below its pre-meal level two to three hours after eating: the quiet half of the meal story, and the half that explains the next snack.
Why it matters
The crash after a spike was folklore until it was measured. In 1,070 adults in the UK and the US who ate 8,624 standardized meals and 71,715 meals of their own choosing while wearing sensors, the size of the dip at two to three hours was a better predictor of hunger and of what people ate next than the peak or the two-hour area: a larger dip went with more hunger at two to three hours, a shorter wait until the next meal, more energy eaten in the following hour and more across the whole day (Wyatt 2021). The correlations were modest (0.16 to 0.27), as they are for most things that drive appetite, and they were directionally consistent in both cohorts. For a person trying to eat less, the dip is the meal figure that matters most.
What moves it
A fast, high rise is usually followed by a deeper dip, because the insulin that answered it overshoots; so the same things that reduce the peak (fiber, protein, fat, a smaller portion, movement after eating) reduce the dip. Whether your breakfast or your dinner dips you more is a question your own record answers after a few repeats.
How to measure it well
The window runs from two to three hours after the meal log, so nothing else should be eaten in that time; a snack at the two-hour mark hides the dip. Log your hunger when VT asks: the appetite ratings are how the dip's meaning in your own record is checked.
How Vitality Tracker uses it
Shown with the peak and the iAUC for every logged meal, and read beside your appetite ratings and the time until your next meal; the meal library can be sorted on it. The Weight Loss Plan reads the meals that dip you. Not a Vitality Score input.
How far to trust the number
Calculated from measured readings at the lower end of the sensor's range, where lag and the occasional compression artifact live; a dip that repeats across days is real, a single one is a question.
Sources
- Wyatt P, Berry SE, Finlayson G, et al. Postprandial glycaemic dips predict appetite and energy intake in healthy individuals. Nat Metab 2021;3:523–9. doi:10.1038/s42255-021-00383-x.