Background: Reductions in eating rate are recommended to prevent and treat obesity; yet, the relation between eating rate and energy intake has not been systematically reviewed, with studies producing mixed results.
Objective: Our main objective was to examine how experimentally manipulated differences in eating rate influence concurrent energy intake and subjective hunger ratings.
Design: We systematically reviewed studies that experimentally manipulated eating rate and measured concurrent food intake, self-reported hunger, or both. We combined effect estimates from studies by using inverse variance meta-analysis, calculating the standardized mean difference (SMD) in food intake between fast and slow eating rate conditions.
Results: Twenty-two studies were eligible for inclusion. Evidence indicated that a slower eating rate was associated with lower energy intake in comparison to a faster eating rate (random-effects SMD: 0.45; 95% CI: 0.25, 0.65; P < 0.0001). Subgroup analysis indicated that the effect was consistent regardless of the type of manipulation used to alter eating rate, although there was a large amount of heterogeneity between studies. There was no significant relation between eating rate and hunger at the end of the meal or up to 3.5 h later.
Conclusions: Evidence to date supports the notion that eating rate affects energy intake. Research is needed to identify effective interventions to reduce eating rate that can be adopted in everyday life to help limit excess consumption.
Alex’s notes: Observational studies have reported that eating quickly may lead to obesity. We have all had moments where we stuff our face with more food than we can chew, and it seems like one saying that has existed forever was that it takes 20 minutes for the stomach to tell the brain it is full. But what does eating speed actually do? We know there are numerous biofeedback mechanisms that control hunger, and this review and meta-analysis sought to assess whether there is evidence that supports the proposition that eating rate affects energy consumption and hunger.
The studies included were controlled laboratory experiments on human subjects without eating disorders. 22 studies were ultimately included for review, and a statistically small to medium-sized effect was observed that showed a faster eating rate increased energy intake. Yet hunger was not influenced, which is likely due to the fact that hunger is a result of learned meal timing. That is, you tend to get hungry around your usual feeding times.
So why does eating slowly result in less food and energy intake? Well, as mentioned earlier we have several biofeedback mechanisms and eating speed and chewing time may influence satiety hormones. A fast eating rate is directly related to a lower duration of sensory exposure of food, and increasing the number of bites or sips, while keeping eating rate constant, leads to lower energy intake. It is entirely possible that we associate the number of sips, bites, or chews with the feelings of fullness that bring a meal to an end, which is in line with the current meta-analysis that found that altering eating rate influenced food intake but not hunger. Indeed, simply chewing more decreases energy intake in obese and lean men.
So given the above, it appears prudent to focus on your meal and enjoy your food if you want to control energy intake. Eat slower, chew more, and let the body do the rest. That said, future research will definitely need to address the magnitude of this effect because personally, all slow eating does for me is make the meal take longer to eat – the amount of food doesn’t change. Then again, I track what I eat so that is obviously something to consider.