Hunger and Eating Digestion The purpose of eating is to provide the body with molecular building blocks and energy Enables us to get energy into the body Digestion breaking down food and absorbing its constituents All of the nutrients we need to survive and have energy Processes of Digestion Where food enters the system through the mouth Glands that enable food to make its way to the stomach Parotid gland near your ear Secretes enzymes that enable the breakdown of starches Salivary gland Prive lubrication to enable to chewing process to separate the food in our mouths Food is now broken down easily to make its way to the stomach Now that it is in the stomach there are many enzymes and acids to allow the food to be further broken down Hydrochloric acid secreted by the lining of the stomach Helps break food down into smaller particles Pepsin released by the stomach lining Breaks down protein molecules into amino acids While the food is in the stomach it slowly begins to pass through the pyloric sphincter looks like a band around the end of the stomach and the beginning of the small intestine The sphincter opens and closes and regulates how quickly food passes from the stomach into the small intestines Very little of the nutrients is absorbed by the stomach There are a few things that start to be absorbed but most are absorbed by the small intestine The small intestines are broken up into 3 segments The upper part where food passes first is called the duodenum The middle part is the jejunum This is where a majority of the absorption of the nutrients takes place The last part is called the ileum This is where some of the remaining vitamins and minerals are absorbed Energy nutrients fats sugars amino acids are not absorbed here As food is being passed through the small intestines we have various types of other enzymes that are now released by the gall bladder and the pancreas and they enable further breakdown of proteins into amino acids complex sugars broken to glucose and fats broken to a form that can now be absorbed and passed through the walls of the duodenum and jejunum so the fats can be stored for later use Energy Delivered Lipid fats and fatty acid absorbed and saved for later Amino acids proteins absorbed Glucose Fats that we consume are broken down into smaller components that can be Broken down by the stomach and small intestines into amino acids then Starches carbohydrates and complex sugars are all broken into glucose A form that also can pass through the intestinal wall and can be stores Energy Stored Energy is stored in our bodies in 3 different ways Triglycerides are fats most of our triglycerides are stored as adipose tissue Adipose tissue fatty tissue and a majority of this is found under the skin we have some other types of adipose tissue that can be found internally visceral fat where it can build around the organs inside the abdomen 85 of our energy storage is in the form of triglycerides Proteins are stored in muscle tissues 14 5 of all energy that we store is through proteins Glycogen stored in the liver Makes up 0 5 of our energy storage There is an order in which our body taps into our stored energy The first place targeted to pull out and convert the stored energy into sugar is from the liver Glycogen Since so little of our energy is stored through glycogen we don t deplete it when we need stored energy The conversion from glycogen to glucose is very quick While this is happening our body is also tapping into Triglyceride Second placed targeted for stored energy is fats Takes longer and more metabolic steps to turn triglyceride into sugar They have to be broken down into fatty acids then broken into ketones then can be processed and used or converter further into glucose Once triglycerides are being converted we stop using glycogen Once fats are depleted the last thing tapped for energy is Protein Often takes days before the body breaks down muscle More energy is stored as triglycerides because of the size amount of energy that can be released from them 1gram of triglyceride stores twice as much energy as glycogen Triglycerides do not attract water If we had the majority of energy storage as glycogen we would weigh 500 pounds to have enough energy for everyday activities Phases of Metabolism How Much We Eat Satiety Signals food available Satiety we are in a motivational state where we stop eating while there is still Not where you choose not to eat or hold back from eating because there is not enough food or it is unavailable Still have food available and have the option to keep eating but you feel full satisfied Important distinction when there is limited availability not satiety Some are based on peptides or chemicals in the brain How much what kind of food we eat Lots of satiety signals Food in gut Glucose in Blood After consuming food people tend to begin to eat less and eat less which ends the meal As you consume more food you are less likely to continue eating and continue eating in high volumes increasing satiety signals As we are eating food and digesting through the small intestines all the various fats carbs and sugars all slowly absorbed and trigger increased release of insulin A phase of metabolism where you have higher levels of insulin being triggered because you are eating As your glucose levels rise with more insulin slowly get a satiety signal from glucose and insulin Volume of Food Cannon Washburn 1912 Larger meal more food in your stomach causes the stomach to expand as it expands that sends the satiety signal Eating smaller meals no stomach expansion with fewer satiety signals Tested in 1912 wanted to determine whether the theory was true Felt the only way they could test was to test themselves Expanding your stomach relax drives hunger Washburn swallowed a balloon on a tube until it hit his stomach Once swallowed Cannon inflated the balloon in Washburn s stomach When the balloon was deflated he would indicate if he felt hungry or not Cannon blew up and deflated the balloon multiple times originally thought Nutritive Density of Food Determined when the balloon was inflated pressure on stomach walls no indication of hunger When the balloon was deflated he felt hungry They thought this supported the idea that pressure on the walls of the stomach is what satiated hunger It was not just the pressure it was whether or not there were contractions that were possible hunger signals When the stomach is inflated it is not able to contract as it