thefunnyshapedwoman.blogspot.co.uk/2011/05/foremilk-and-hindmilk-in-quest-of.html
kellymom.com/bf/got-milk/basics/foremilk-hindmilk/
thetruthaboutbreastfeeding.com/category/research/forehind-milk/
www.ncbi.nlm.nih.gov/pubmed/16510619
www.nancymohrbacher.com/blog/2010/6/27/worries-about-foremilk-and-hindmilk.html
www.parentingscience.com/infant-feeding-schedule.html
Leafmold, the above links should give you the picture :)
Basically, the fat content of human milk varies with the degree of fullness of the breast.
Full breasts = proportionately less fat in the milk; emptier breasts = proportionately more fat in the milk.
As the breast empties, the milk gets fattier. This does not mean that babies always have to feed a long/longer time to get the fattier milk, therefore they should be placed on a four-hourly schedule to make sure they feed for a really long time instead of 'snacking'. Frequent, 'cluster' feeds do get fat into the baby, because the breasts' degree of emptiness rises (and also, therefore, so does the fat content).
Babies on a four-hour schedule, with mothers who have a generous milk supply which survives this regimentation (and some mothers do have this) may well manage to get what they need because they will adjust their volume of intake to get the fat they need (as long as the mother isn't doing something crazy like taking them off after an arbitrary length of time).
But mothers without a generous milk supply who decide to feed four-hourly may find the reduction in volume produced with this sort of schedule is very damaging for breastfeeding ie they don't make enough milk and their babies fail to grow.
We know (from testing babies and testing milk and tracking babies' growth) that babies do adjust their fat intake, and when babies are fed responsively, they may feed at different intervals (ie individual babies feed individually), and their fat intake is more or less the same overall....so the mother's body and the baby's needs work together, pretty much.
It makes no sense at all to say the baby who feeds four-hourly gets 'more hindmilk' and that this is a better thing and therefore should be generally recommended.
Hope this explains things.