Eating Rate
Eating rate is how fast a meal is eaten, and the claim usually attached to it is that eating slowly means eating less. The claim is half true. Slowing people down does reduce how much they eat at that meal, by a moderate amount and consistently across the different methods used to slow them. It does not make them less hungry afterwards, and the pooled evidence finds no relationship between eating rate and hunger either at the end of the meal or for several hours after it. This page describes a research finding and is not an instruction about how anyone should eat.
What it is
The evidence base is a systematic review and meta-analysis by Eric Robinson and colleagues, published in 2014, which pooled twenty-two studies.
Two results come out of it and they point in different directions. Slower eating went with lower energy intake at the meal. The pooled difference was moderate, it held across the various ways studies had of slowing people down, and there was substantial variation between studies, which matters for how confidently any individual case can be predicted.
And eating rate had no relationship with hunger, either immediately at the end of the meal or at follow-ups running to three and a half hours later.
The usual proposed mechanism for why slower might mean less is gastric stretch, the idea that fullness signals need time to arrive and a fast eater outruns them. That mechanism would predict the first result and would also predict an effect on later hunger, which is not found.
In effect
Where this bears on ordinary experience is the afternoon slump in appetite control after a large lunch. The intuitive account is that the lunch was eaten too fast. The pooled evidence says eating rate is not what determines how hungry someone is three hours later, so that account is looking in the wrong place.
What eating rate does influence is the size of the meal itself, which is a different lever and a real one. It sits alongside portion size, which is better evidenced as an influence on how much gets eaten, and alongside meal memory, where the attention manipulations are themselves inconsistent.
The honest summary is that the half of the popular claim that survives is the half about the meal, and the half that fails is the half about afterwards.
What it does not say
It does not say that eating slowly reduces hunger. The pooled analysis specifically found no relationship, out to three and a half hours.
It does not say that everyone eats less when slowed. The between-study variation was substantial, so the pooled moderate difference is an average across quite different results.
It does not establish the mechanism. Gastric stretch is the usual explanation and it does not sit comfortably with the absence of any later effect.
And it is not advice. This publication does not tell readers how fast to eat, and material touching on health is handled under the house standard for such topics.
Sources
- Robinson, E., Almiron-Roig, E., Rutters, F., de Graaf, C., Forde, C. G., Tudur Smith, C., Nolan, S. J. & Jebb, S. A. (2014). "A systematic review and meta-analysis examining the effect of eating rate on energy intake and hunger." American Journal of Clinical Nutrition, 100(1), 123-151. 22 studies; pooled standardised difference 0.45, 95% CI 0.25 to 0.65, with substantial heterogeneity; no relationship with hunger at the end of the meal or up to 3.5 hours later.