Apols bonj...not been online for a while...busy, busy!
Well I'm a Food Scientist rather than a nutritionist, though I have a reasonable comprehension of body function and chemistry.
It's a good question, they used to say:
Breakfast like a King
Lunch like a Lord
Supper like a Pauper...
I take Jules point, if we need 2500 cals per day does it matter when we eat them...well maybe it does...but Im no expert in this foield but my take is like this...
The body is a complex interplay of various chemical pathways that are very dynamic and sit in an ever shifting equilibrium depending on what the body is doing at any particular moment.
So, it seems sensible to have a large slowly digested meal at the beginning of the day to give yo the fuel for the most active period. In a perfect world the food you consumed would top-up the fuel tank at about the same rate and quantity at which you used the energy from the tank. The reality is probably somewhat different with energy supply from food being out of phase with energy requirement. So for example a long-distance cyclist will burn more fuel when cycling than he is eating, so he draws upon glycogen and fat reserves...this debt needs to be repayed at the end of the day. Hunger is the signal the body provides to tell us to eat...(if close to bonking then it'll make us to crave sugar or anything sweet). So, we eat and the fuel stocks are re-plenished...assuming the hunger signal ensures we don't eat more than we need...my guess is that in most cases we will over-cal and the excess converts to more fuel storage, and the most convenient form is fat.
Insulin is a major mediator in fuel storage and mobilisation.
My hunch is that consuming a large quantity of food prior to bedtime is more likely to lead to weight gain. My thinking is that in going to bed, metabolism slows down, less heat genetration, mental and muscular activity virtually ceases (the 3 big power consumers), the body will digest the big dinner, insulin surges and as the immediate body needs for fuel are low then more of the calories will be converted to storage molecules i.e fat than if the same meal was consumed for breakfast when the immediate calorie usage rate is much much higher.
If you have a big meal before bed and the calories are stored as suggested, will they be utilised in the morning...well maybe, and some of the nights stored excess fuel will be utilised but the body will start giving the hunger signals and asking for more fuel as well. On balance I think eating late at night is more likely to lead to weight gain than eating at another time, primarily because of the powerful role of the Insulin storage response and the hunger trigger.
Now as Jules suggests if you expel 2500 cals per day and consume 2500 cals per day, does it matter when you consume them? Where is the problem? Well, IMO,the problem is that by eating late you will spend much of the day feeling hungry and maybe feeling lethargic as stored fat being mobilised is your main source of energy (it's important to note that whilst sugar and protein can be converted to fat, fat cannot be converted back to either), then hunger strikes and in most people that will lead to increased daily calorific intake.
The idea of "grazing" throughout the day seems appealing, better balancing energy input and output and reducing the big insulin swings which lead to excess fat accumulation (and lethargy) when calorie intake becomes in excess after a big binge.
Can't comment on your mother notion about motions...I don't think there is any evidence (Though I may be completely wrong) that links night-time eating with bowel cancer issues. Good digestive transit from a high enough fibre diet, not overdosing on red-meat and having healthy gut flora seems to be the important points.
Flip, I've no idea if that makes any sense to you, but it's my best go at a reasonably short answer!
