In response to requirements by many educational organizations, the Organization for the Research of Giantesses And Similar Monstrosities (O.R.G.A.S.M.) has been asked to compile the following report on the class Bigass Girlswhoeatus, or Giantesses, as they're traditionally called.
Field research into this type of creature is limited, as very few of those who encounter giantesses live to share their observations, and so we shall have to infer much about giantesses via what we can find out without direct observation.
Reports generally place the average giantess between 200 and 400 feet tall. For simplicity's sake, we shall take a median example of a 300-foot giantess.
First is the question of bodymass. The average woman is of what equates to roughly a 5x1x1' build, giving us a simple size of five square feet. Weight is highly variable, but for simplicity in calculation let's place it at 120 pounds. This gives us a weight to size ratio of 24 pounds per square foot.
Now assuming all dimensions are increased equally, as seems to be the case, our giantess would now be in the vicinity of 300x60x60', a size of 1,080,000 total square feet (!). Assuming the same 24 pounds per square foot, this gives us a bodyweight of 25,920,000 pounds, or nearly thirteen thousand tons.
Now, say your average human consumes three pounds of food per day. Applying the same percentage increase in bodyweight for our giantess (2,160,000%) gives us a new food intake of 64,800 pounds, or the equivalent of 540 whole, petite females.
We could place this at 180 females per meal, on average, which poses a problem--due to people's tendency to scatter and run, it would be somewhat tedious to chase down, catch and eat 180 women three times a day to avoid becoming malnourished. This would go some distance to explaining why many giantesses opt to eat women in convenient 24-pack form (Also known as municipal buses) and even go so far as to uproot and swallow entire buildings (It is assumed they are able to digest the structural features of the building, though the prospect of an examination of giantess stools to check for, say, bent I-beams and intact building supports wasn't met with the highest level of enthusiasm).
From the perspective of the victim (Which we all, unfortunately, seem to share) the giantess is a terrifying prospect. The normal 1-inch esophagus of a human female would be a tunnel five feet wide for a 300-foot giantess, making the swallowing of a whole, live human an easy and even practical process. Their stomach would be a cavern the size of a parking garage, and their massive muscles may well be strong enough to crush a parked car between the folds of the stomach walls.
Little is known about the strength of the enzymes and juices within the giantess, but it can safely be assumed from experience that they can digest entire populations in the same time it takes one of us to process an average hamburger--from this, we can only conclude that they are fearsome indeed, leaving at best a life expectancy of six to twelve hours for those unfortunates who are ingested (Realistic estimates may be even less).
The intestines of an average giantess would likewise be over a half a mile long and four to six feet in diameter, allowing for the possibility of a human-sized creature being passed into the intestines while still alive--the bearing this would have on it's being digested is unknown, but presumably would be rather small in the long run (No one has been known to survive a trip through a giantesses digestive tract, and few can say whether the intestine would be any less unpleasant than the stomach). It is believed that victims are digested as thoroughly as any meal, leaving little more than feces (In mounds five feet high and as many as thirty feet long--in the words of Thomas Jefferson, "That is one big pile of shit").
Needless to say, this new information reveals giantesses as an even greater threat than previously believed, particularly in the case of the larger ones. Entire small towns could be devoured to satisfy the nutritional needs of even one large giantess. Even an average one may have to gulp down an entire apartment building and digest both the building itself and every last denizen inside just to hold her until lunchtime.
Unfortunately, history has also shown giantesses to be all but invulnerable to any and all conventional weapons, and they seem to take a particular pleasure in eating those who shoot at them with tanks...So it is the resigned recommendation of we at O.R.G.A.S.M. that we all act as innocuous and low-profile as possible and go down like good little morsels if indeed we are the unlucky chosen of a giantess. After all, running only makes them hungrier, and nobody wants to piss them off enough that they decide to chew...