This suggests that the oral processing of foods, which includes the physical feel of food in the mouth as well as its taste and smell, provides the brain's satiety/hunger centers with important cues about how many calories have been consumed. When this oral processing information is eliminated by tube feeding it takes more food and calories going to the stomach via a tube to leave people feeling as satiated as they would have been consuming it normally.2 The importance of oral processing cues to increasing the satiety/calorie ratio is further suggested by the relative reduction in satiety/ calorie seen for the same energy intake consumed as a beverage rather than as a solid food.3 Oral processing cues also appear to be reduced when the same food is consumed more quickly.

Researchers recently looked at the levels of satiety hormones in the blood after consuming the same food quickly or slowly. They measured the levels of two gut hormones involved in the satiety process and found peptide YY (PYY) and glucagon-like peptide (GLP-1) were significantly higher for several hours after the subjects consumed ice cream slowly (30 minutes) then when they consumed the same amount of ice cream rapidly (5 minutes).4

Higher levels of satiety hormones from the gut along with increased direct sensory cues from the mouth to the brain via sensory neurons may be why eating more rapidly may increase the risk of excessive calorie intake and weight gain. More recently Dr. Zilstra from the Top Institute for Food and Nutrition in the Netherlands provided yet more data suggesting that eating more slowly may increase the amount of satiety per calorie.

Dr. Zistra fed 22 healthy subjects a chocolate custard test meal varying the "bite size" and the interval between bites. The custard was fed through a tube in order to precisely control the amount per "bite" and the time interval between "bites". The results showed a significantly reduced calorie intake with smaller "bites" and increased oral processing time.5

A diet containing minimally processed foods that have a low calorie density and a high fiber to calorie ratio tends to provide more satiety per calorie than highly refined and processed foods high in fat and calorie dense for many reasons. Foods that require more chewing typically provide more satiety per calorie than more processed foods and part of the reason may be increased oral processing time and increased release of gut satiety hormones.

However, even if it is true that when eating calorie dense, highly processed and refined foods that they may provide a bit more satiety per calorie if you take smaller bites and consume them more slowly this strategy alone will not likely be sufficient to prevent the excessive energy intake seen in most people who consume a modern diet.

Bottom Line: Evidence continues to mount that suggests the typical modern diet full of calorie dense, highly processed foods and drinks that require little or no chewing may be promoting excessive calorie intake and obesity. Part of the reason may be the reduced oral processing time and satiety cues people get when modern foods spend little time in their mouths. However, even if oral processing time and the speed at which people eat impact ad libitum energy intake, it is doubtful that focusing on these variables while ignoring the calorie density and the amount of fiber in their diet will dramatically reduce obesity. Instead focus on what people are eating and reduce their consumption of calories in beverages. Those strategies are far more likely to significantly increase satiety per calorie and result in weight loss without any need to count calories than focusing on other behavioral strategies to slow eating and increase oral processing time.

By James J. Kenney, PhD, RD, LD, FACN.?

References:?

1. Cecil JE, et al. Physiol Behav 1999;67:299-306?

2. Lavin JH, et al. Intl J Obes Relat Metab Disord 2002;26:80-6?

3. Kokkinos A, et al. J Clin Endocrin & Metab, doi:10.1210/ jc.2009-1018?

4. Zilstra N, et al. Am J Clin Nutr 2009;90:269-75

For more information on satiety, go online to foodandhealth.com and click on CPE courses. Scroll down to weight loss and you can read Dr. Kenney?s comprehensive reviews on the glycemic index and fad diets that both discuss and illustrate satiety. You can read all of his articles for free. CFFH subscribers who are RDs can take this online CPE course for a discounted rate.