I have what I'd guess is between 20 and 30 lbs of fat left to lose to get a figure I'd be satisfied with, so I try to keep carbs relatively low. I don't count, but I would estimate I generally land on the low end of the 50-100g/day range Sisson suggests.
However, as we all know carb consumption drives insulin up, and insulin leads to storage of both glucose and fats.
So, would it be a good idea to separate fat intake from carb intake to prevent storage of more fat? Or when you're eating LC, particularly foods with a lower glycemic index, is it not enough to worry about? Or does eating the fat with the carb actually buffer the insulin increase?
I think the only real problem with mixing carbs and fats is when you do so via processed food ... lots of refined sugars & grains and unhealthy fats is no one's prescription for health!
So IMO, the answers to your questions are no, you don't need to separate the two, no, if you're eating LC, it's not much of an issue, and yes, eating fat is thought to help slow digestion (why they say if you're gonna eat bread, eat it with butter or olive oil).
BTW, another plus for fat with your meals is that it can help you absorb fat-soluble vitamins.
Much more important than not mixing carbs and fat is not mixing carbs and exercise. The insulin spike will force a mitochondrial substrate change toward glucose oxidation and both reduce lipolysis and intercept the glucose before it gets partitioned as glycogen. Exercising with low insulin levels is of paramount importance whether or not you are doing low carb.
Personally I separate carbs and fats. 1) is that fat reduce efficiency of glucose uptake and transport into the muscle cells and 2) I notice that I stay leaner without mixing fats with carbs.
I think the main thing you need to worry about if your trying to lose weight is the food reward synergy between fat/carbs that makes them extremely stimulating and often leads to overeating. If you can control the portions I don't see any problem in mixing the two for the most part.
IF they are paleo carbs and fat mixing the two are a great idea for weight loss. If they are in processed food its a real bad idea because of the fructose and O6 content is additive to the hypothalamic damage and likely compounded by the hydrolyzed veggie protein likely added.
I want to bring this question up again with something more specific- for an emphasis on leaning out (just a little bit of extra fat left), I train fasted for ~45 min-an hour. I eat low carb in general, but I am wondering- PWO, protein + carbs only, no fat? Or stick with just the fat and protein as usual? I'm not looking to do a full leangains carb day on training days. I will stay fairly low carb every day, except PWO, just wondering about including fat in that meal or not.
I will just tell you what I do. I personally do not eat carbs with fat, as I have both read that fat interferes with glucose uptake and experienced that I stay leaner when I separate carbs from fats. This is just me, personally though. WE are all different and I specifically do not eat a very high fat diet- I use some avocado and olive oil, and that's about it, usually.
Experimenting is hard when you are above a certain level of body fat. I know what works for my body within a couple hours to days because of my muscle/fat ratio- a .5% change in body fat over a day is noticeable, whereas a .5% change over a day is unrecognized in a heavier set person. I notice how a food impacts my body immediately, and that is what has served me as to how I like to eat to maintain a certain level of fitness. Who knows though, fat with carbs may be the best thing for you, it's just not for me.