This morning a question occurred to me so i thought id put it out there for you guys:
One of IF's positive points that ive heard mentioned many times is its blunting of insulin. However, i've heard many times (this is even mentioned by Taubes in GCBC) that insulin may be generally higher in the mornings for most people.
So what i cant seem to get my head around is that since sleeping is essentially IFing (to a degree) how come insulin would be higher in the morning.
Cortisol levels are normally highest in the morning and cortisol promotes gluconeogenesis. Which means the liver makes and releases more glucose into the blood. Insulin rises in response to blood glucose.
After a meal, insulin can increase 3-4 fold for a period of about 4 hours. http://heartscanblog.blogspot.com/2010/03/timing-of-blood-sugars.html
The elevation of insulin in the morning is much smaller.
The argument for IF goes something like: condensing your eating into say a single 6 hour period results in lower average insulin levels over a 24 hour period. Instead of 3-5 meals that keep your insulin levels elevated all day (12-20 hours) with a 4-12 hour break, you have maybe 8-10 hours of elevated insulin levels separated by 14-16 hours of basal insulin levels.
One thing that I have yet to see is evidence that IFing increases insulin sensitivity of cells over a long period of time. So far, all research I have seen shows increased insulin sensitivity right after the fast. But how much does this help if the sensitivity goes right back to normal later in the day?
Another issue I have is that so far all the research I have seen has been on people eating normal carbfilled foods. If the goal is a break from high insulin, then eating low carb already provides that and if sufficiently low carb and consistant, it provides that on a much more consistant basis than does IFing. What I would like to see is research on fasting in those who already eat lowcarb and whose insulin is normally not spiking at all in the first place. Would such a person still benefit greatly from intermittant fasting? Would such a person still have increased insulin sensitivity if this person already had increased insulin sensitivity to start with because of low carb?
Seems to me, at some point, there would be a point of diminishing gains. The cells are only going to get so much more insulin sensitive and at some point they will reach the preferred level and there should be no more increases in sensitivity at that point. Seems to me, increases in insulin sensitivity are only good if you assume that your cells are currently not yet at the preferred level. If your insulin sensitivity is already at good levels, what do you gain by IFing?
(Not to say I am against IFing, I am just not sure if I am really positive about the benefits being there for everyone in all situations. I have not yet seen the research to have that much belief and am waiting to learn more. IMO, IFing is one area of paleo in which I don't feel the research is really fleshed out yet.) -Eva