A clarification that I did not think needed to be addressed, yet still does the debate of the issue continue in a manner that suggests that which is not proven: all foods provide adequate sustenance(calories) that when consumed in appropriximate quantities(say the basis of 2,000 daily) will sufficiently afford & attain a general sensation of complete nourishment or well-being(feeling full).
The above statement is false. It is a fallacy to equate the amount of calories in any food to that of another in order to comparably define its nourishing factor. Of course different foods provide different nutrients in varying degrees, but it is not suffice to state that once one reaches the plateau of 2,000 calories, or some fraction of that during any one meal, can one adequately resolve that you, me, or anyone else will feel fully-satisfied after consumption.
E.g. Waking up, subject Amanda, subject Billy, and subject Colleen decide to prepare their respective breakfasts before tackling the day ahead of them.
Amanda prepares toast, grits, orange juice, milk, and a serving of ham with honey. Caloric Content of food: 750
Billy on the other hand, goes to the backyard with a basket to hand-pick his meal; eight apples sliced, served baked along with a cup of sugar water. Caloric content of food: 750
Colleen opts to just drink coffee with cream & sugar to go. She pours herself a pint of hot brew into a thermos. Caloric content: 750
Intepret the above as you see fit. I'll just offer up that whether I decide to down cans of coke every waking hour today, I'll amass calories, but I will not feel full regardless of what the nutritional facts state in terms of the extemely high caloric content, among other things replete and devoid, within this concoction. Calories are not a universally equal or even accurate measurement of satisfying or fulfilling one's hunger. It is just a signpost; what you see is not necessarily what you will encounter. Certain foods are more apt to sate hunger by providing a full-feeling to our neural receptors & abdominal constrictions.
Research: Feeling full
"Eating behaviour is influenced by hunger and the rewarding properties of food (which drive us to eat) and by satiety signals (which tell us we're full), but little is known about how the brain integrates information from these pathways.
Suspecting that the fat-derived hormone leptin might be involved, Sadaf Farooqi and Paul Fletcher, both Wellcome Trust Senior Fellows in Clinical Science from the University of Cambridge, studied two teenagers with congenital leptin deficiency. People with this condition eat excessively - even bland foods - but can be treated with leptin replacement therapy.
Functional magnetic resonance imaging was used to measure the subjects' brain activity as they were shown images of food, both before and after a week of leptin treatment.
Leptin altered brain activity in the ventral striatum, a brain area associated with pleasure and reward. The hormone also seemed to help the subjects to discriminate better between bland and tasty food. Before treatment, they strongly liked nearly all foods shown (from cauliflower to chocolate cake); after leptin replacement, the average scores fell.
Leptin was also important in linking the liking of food with hunger. Brain activation in a specific striatal region was triggered by images of well-liked food, whether the leptin-deficient subjects were fasting or full. In healthy controls - and in the treated subjects - the response was seen only when people were hungry.
The results suggest that leptin acts on the brain to decrease the perception of food reward and boost the response to satiety signals after eating."