In a study published in the Journal of American Dietetic Association (1975, Vol. 67; 344-346), comparing obese to non-obese (31 adult males & females), it was found that the obese spend less time consuming their meal and they chew each mouthful of food in shorter time than the non-obese. The authors observed that these “fast eaters” did not sense oral satiety. Researchers looking at the satiety-hunger feedback mechanism discovered that while stretch receptors in the gastrointestinal tract bring about short term inhibition of eating, it is the elevation of blood glucose that plays a long-term role in directly stimulating satiety. (American Journal of Surgery, 1987, Vol.153; 265-269)
Data collected from National Food Consumption Surveys in 1977, 1989 and 1998 with a total of 63380 participants confirmed that portion sizes have indeed increased over the years as has the incidence of obesity in the US. The authors state that “simply educating the public about which foods to eat or not to eat is not enough, as an equally important issue is the quantity of food being consumed.” The authors noted that even portions consumed at home have increased—a shift that indicates marked changes in eating behavior in general. They contend that the best way to encourage eating smaller portions is if food portions served inside and outside the home are smaller. (JAMA 22/29, 2003-Vol.289, No. 4; 450-453.)
Gastric-emptying rate of fluids from the stomach into the intestine is influenced by a variety of factors including, but not limited to, fluid temperature, osmolality, sodium content, pH, calorie content and electrolyte content. In a study using eight healthy, college-aged males, researchers evaluated the difference absorption rates of different carbohydrate solutions finding that an 8% carbohydrate (glucose-fructose) solution provided a more rapid delivery of glucose to the blood than other carbohydrate solutions. (American Journal of Clinical Nutrition, 1990; 51:1054-7.)
For people exercising, replacing water and restoring depleted glucose stores is facilitated by drinking a beverage that contains a source of carbohydrate. In a study of eight healthy males, researchers compared different solutions to determine which concentration facilitated both absorption of water and absorption of glucose (Medicine and Science in Sports and Exercise, 1995; 27: 1607-1615.) The goal is to maximize absorption of water to prevent dehydration but also to maximize carbohydrate absorption to raise circulating blood sugar to meet the needs of the exercising body. The optimal solution to meet both needs is a 6% solution. However, in order to raise the blood sugar up more quickly and turn off hunger, an 8% solution gets the carbohydrate in faster. Observing eating behavior of 100 customers in a fast food eatery resulted in the conclusion that obese subjects took more bites , performed fewer chews per bite and spent less time chewing than did non-obese subjects (Journal of Consulting and Clinical Psychology, 1975, Vol. 43, No.2, 123-125)
“Accelerated ingestive rate”—the scientific way of saying fast eating has been noted in a study comparing lean to obese men and women in which obese persons both male and female exhibited no significant change in ingestive patterns at the end of the meal unlike the lean subjects who slowed down their ingestion rate toward the end of the meal. (Physiology & Behavior, 1981; Vol.27: 649-658). Saliva has multiple essential functions that contribute to taste perception, enzymatic digestion and esophageal clearance according to a report in Oral Diseases (2002) 8, 117-129 but in order to reap the benefits of saliva, chewing must take place. Chewing or “mastication” of food stuffs brings on the saliva and once incorporated into the foodstuff assists by enzymatically breaking down the food into smaller particles. Additionally, the water in the saliva helps to lubricate the food making it easier to swallow. “Swallowing of food most likely occurs when two thresholds are satisfied, a food particle size threshold obtained by chewing, and a lubrication threshold by the flow of saliva into the oral cavity.”
In one of several studies reported by Spiegel (Neuroscience and Behavioral Reviews 24 (2000) 229-237), it was determined that depriving individuals of food and then providing highly palatable foods was not a recommended combination because more food was consumed. “The combination of food-deprivation (no breakfast or lunch) followed by eating a dinner of highly palatable foods stimulated the most intake in both obese and lean subjects.”
Distending the stomach stimulates gastric receptors, which triggers vagal (nerve) discharges that activate hypothalamic neurons [in the brain] and induce the feeling of satiety. These stretch receptors may not be fully stimulated until the stomach has been distended to a certain proportion of its limit. With a larger gastric capacity as observed in a study of bulimic women (American Journal of Clinical Nutrition, 1992;56:656-61), increased intake may be required to stimulate these stretch receptors and signal fullness. Researchers found that it took a significantly larger quantity of food to produce satiety in the bulimic women with the larger capacity stomach as compared to those produced by the smaller meal intakes in normal subjects.
Twelve healthy volunteers chewed mouthfuls of either bread or spaghetti to help researchers determine that the physical and chemical degradations of solid foods during oral digestion may influence the entire digestive process (British Journal of Nutrition (1998); 80: 429-436). By adequately chewing food, blood glucose response was more immediate than when food was not sufficiently chewed.
Does an extremely obese person have a larger stomach than a normal weight individual? In a study evaluating stomach distention, 16 extremely obese persons were investigated before planned gastric surgery for weight reduction. Researchers Granstrom and Backman (Acta Chir Scan 1985, 151:367-370) determined that the subjects seemed to tolerate greater distension of the stomach as compared to persons with normal body weight. Adaptation to the eating pattern [larger quantity and more frequent eating] may result in a larger stomach capacity. Additionally, Backman in another study determined that the small intestine was also found to be significantly longer in extremely obese persons than in persons with normal body weight. The greater length allows for a greater chance to absorb more energy-yielding nutrients (calories).
Finally, 80Bites is influenced by the Japanese idea of “Hara hachi bu“, which means “stop eating when you are 80% full”. In a study of centenarians in Okinawa (SCAN, vol.22, no.1, Winter 2003;14-18) researchers determined that the Okinawan diet which is low calorie and low quantity generates few free radicals, thus minimizing potential damage to cellular machinery thereby resulting in slower aging at the cellular level. Researchers observe that “serving sizes are about half of those in the US, making Okinawans less likely to overeat.