The urge to eat is governed by many factors and in spite of tons of papers published over the years we are still groping in the darkness regarding the precise mechanism that works in human beings to yearn for food. While the level of glucose in blood is one of the indicators that influences hunger, there are other physiological and biochemical changes occurring during pre and post food consumption that can drive the consumers to the food counter. Satiety is known to be caused by fullness in the stomach as a result of higher volume of food but it can be short lived if the diet contains too much water and less solids. Similarly the ease of digestion of the food consumed in the GI tract can post pone the eating session significantly. Glucose and other sugars which are absorbed fast can create more urge to consume more foods.
The phrase 'Hunger pangs' is used commonly to describe contra indication of empty stomach. Feeling of hunger is related to a desire or a need for food which is caused by psychological and/or physiological factors. It is believed that stomach contraction or lowered blood glucose or lowered body temperature can also trigger hunger pangs in many people. Psychological factors that induce hunger include eating habits, frequency and time of eating, environment etc. All the five senses like sight, smell, taste, color and touch do influence the feeling of hunger whether real or imaginary. Satiety is controlled at the brain as well as stomach levels. The ventromedial nucleus of hypothalamus in the brain generates signal for stopping eating due to satiety while the lateral hypothalamus signals to start eating. At GI level satiety originates from the stomach which controls short term eating. Leptin which is a signaling molecule produced by fat cells is also known to reduce activation in the region linked to hunger while enhancing activation in regions associated with inhibition of heating and satiety.
Modifications in foods can be brought about using modern food technology to induce satiety and reduce eating thus depriving the body of excess calories that cause increased body weight in the long term. Olive oil well known as an edible oil with high nutritional value has been shown to be an effective hunger killer if appropriately modified using emulsion technology which gave to the consumers hundreds of products based on fat and water. Water in oil emulsion type of products like margarine or oil in water emulsions like salad dressings and ice creams are classical examples. Emulsion is a thermodynamically unstable system that tend to separate with time into the original two phases. An emulsifier with appropriate Hydrophilic-Lipophilic Balance (HLB) value, any where between 1 and 20 is commonly used to stabilize different emulsions depending on the proportion of water and oil in a mixture. Those with HLB values less than 9 are predominantly lipophilic in nature while 11-20 are hydrophilic in nature.
Olive oil emulsion using the internationally approved non-ionic surfactant Tween 60 (E491), known chemically as Polyethylenesorbate monostearate was discovered to have the capability to delay hunger and increase the interval between the meals by virtue of delaying digestion of oleic acid in the intestine. In contrast an emulsion using Span 80 or sorbitan mono oleate (E494), another emulsifier which does not have the ability to withstand the strong acidic system in the stomach, was found to be ineffective in increasing the residence time of olive oil in the intestine. Traces of Tween 60 based emulsions were found in the GI system up to 12 hours after ingestion. Oleic acid is converted to the lipid hormone oleoylethanolamine (OEA) which wards of hunger for extended periods. Modern food processing equipment range includes highly efficient emulsifiers like colloid mills which can reduce the droplet size to less than one micron in the final product. Time is not too far away when consumers can have such hunger delaying preparations in the form of popular products like milk shakes or ice creams or differently flavored beverages that can become a part of the regular diet. Probably industry has to gear itself to take up the challenge of obesity more seriously by supporting such scientific innovations by food scientists in their laboratories.