Insulin & Weight/Fat Loss ~ The Long and the Short of It
In the comments of my recent post, On Cherry Picking & Debunking, my "Insulin Warring" partner Todd Becker posted a multi-point commentary. I'll get to the rest over in the comments section in that post when I get a chance, but one of his points hit on something just a little different as it goes to the core of my issue with the insulin hypothesis. (And I'm reminded I'm long overdue for an installment on the IW exchange with Todd)
In any case, here was what I said:
G&K demonstrated absolutely no correlation between fasting insulin and weight change. Therefore fasting insulin is not a factor in determining weight loss.
Your claim that there is "no correlation" between insulin levels and weight looks only at the instantaneous correlation. But fat loss may be a delayed response, as the Woodhouse paper I linked to you indicates. Figures 1 and 2 in G&K suggest that weight either dropped or plateau'd after a slight lag in the few cases where insulin levels approached 10 uU/ml. That the weight loss continued in some cases even after insulin levels begin to increase suggests that weight regain may be a delayed metabolic response.
The G&K protocol used "fasting insulin" as a surrogate for basal insulin. These are not the same thing. Fasting insulin was measured twice weekly at 7-8 a.m. after a 12 hour overnight "fast". But fat loss may depend on how much of the day insulin levels remain very low. Truly low basal insulin levels may take many weeks to establish.
Let's first address the Grey & Kipnis study with a discussion that comes full circle on one concept as regards insulin. But first a little salute to Todd Becker for being one of the few folks Jimmy Moore queried for his blog who appears to have actually read James Krieger's articles. He also did an excellent job, all disagreements I may have with his analysis aside, of addressing James' assertions. So rather than sending you on a trip about the web, in the first installment of his series, Insulin…an Undeserved Bad Reputation, James discusses something that I've repeated often regarding Taubes' theories on insulin. That being that insulin is the fattening hormone. It's not that Taubes gets the biochemistry/metabolism wrong, it's that he takes it wholly out of context. James constructed this graphic shown in the screenshot below:
James precedes this graphic with the following:
One misconception regarding a high carbohydrate intake is that it will lead to chronically high insulin levels, meaning you will gain fat because lipogenesis will constantly exceed lipolysis (remember that fat gain can only occur if the rate of lipogenesis exceeds the rate of lipolysis). However, in healthy people, insulin only goes up in response to meals. This means that lipogenesis will only exceed lipolysis during the hours after a meal (known as the postprandial period). During times when you are fasting (such as extended times between meals, or when you are asleep), lipolysis will exceed lipogenesis (meaning you are burning fat). Over a 24-hour period, it will all balance out (assuming your are not consuming more calories than you are expending), meaning you do not gain weight.
I am in 100% agreement with James' analysis on this point. Essentially one can only consider carbohydrates and insulin "fattening" if one takes the biochemistry/endocrinology out of context. Yes, when insulin levels are high it favors net fat deposition, and low, net fatty acid mobilization. But in normal individuals "insulin spikes" play a rather minor role in basal insulin levels and are balanced out by low basal insulin levels.
Basically James and I point to a fundamental flaw in the insulin hypothesis: Extrapolating the short term (instantaneous) effects of insulin to the long term regulation of body weight.
See where I'm going here? Todd is now saying that in Grey & Kipnis, we're looking at the "instantaneous" picture and ignoring the *possible* delayed effect of lowered insulin. Respectfully, I will say that you really can't have your coconut flour cake and eat it too. Either the rather dramatic fluctuations in fasting insulin achieved by G&K in already obese young women, through dramatic variation in carb content of the diet, impact weight** or not. Either the instantaneous action of insulin that (paraphrasing) "fixes and traps fat" in our fat tissue leads to long term weight gain, or it doesn't. I'm often chided to look at "real life" observations more. There again, some folks (myself included) seem to lose weight very rapidly at first (even after the initial glycogen associated water weight whoosh is over) long before the hyperinsulinemia of obesity has subsided substantially. I contend that Todd's personal experience of delayed weight loss once his insulin finally lowered is diametrically opposed to what the majority of low carbers experience: rapid initial losses that plateau out (often well above a normal weight) after a period of time when their fasting insulin finally comes down.
Let's look once again at the results for G&K:
To refresh, these diets were ~25% protein and either essentially 75% carb or 75% fat. A truer head-to-head of high carb vs. high fat we couldn't get. Todd contended in other comments that the durations of the diets may not have been sufficient either. There are several problems with this, we see no "delayed" response to which he eludes, only continued maintenance or weight loss. That weight loss continued even after fasting insulin was again raised, I suppose *could* be explained by some delayed effect, but here again I'm sensing some mental gymnastics. Tautology girl here (grin) would suggest a simpler explanation: weight loss continued because calorie deficit continued. Where there are some anomalies for the maintainers, there's no consistency. This was the purpose of my constructing the scatter plot of change in weight vs. change in insulin.
I stand by my conclusion, to repeat:
G&K demonstrated absolutely no correlation between fasting insulin and weight change.
In order to even hint at causality, one must at least identify a correlation. Nothing to see here folks.
I remain a bit confused over what the timeframe for a delay might be. In the weight loss group we were talking a month on each diet. They lost weight continually throughout the three months on 1500 cal/day. Beginning with high carb, proceeding through low carb, and returning to high carb. I'm not sure that assessing fasting insulin and weight weekly would qualify as any sort of "instantaneous" picture.
**Before continuing, I have to address the whole weight vs. fat mass thing. Unfortunately G&K only measured body weight, not fat mass. This is what most of us measure on our bathroom scales as well. I've not seen any data demonstrating that the proportion of fat/total mass lost on LC differs from that achieved with other dietary interventions. Therefore, absent additional information, I worded my conclusion carefully, fully aware that fat and weight loss are not the same thing (and I've come across yet another study demonstrating more favorable fat loss with exercise that I'll be blogging on soon, and I'll address the Woodhouse paper at that time if I can get my hands on the full text) .
OK, onto Todd's other point regarding fasting insulin vs. basal insulin. Generally these are the same thing. Perhaps he meant insulin AUC = total insulin exposure. To discuss this I'll repeat the graphic first highlighted here:
This is the 24 hour insulin profile for overweight (avg. BMI 26) women, all consuming a 50% carb diet:
□ = isocaloric 15% protein, ● = isocaloric 30% protein, Δ = ad lib 30% protein (weight loss)
Hmmmm... draw a horizontal line around the 35 line for insulin and you have .... ta da! ... James' graphic!
These subjects had fasting/basal insulin levels of around 10-15. Even the AUC insulin exposure did not differ much. In this study they first replaced 15% of fat calories with protein at isocaloric weight maintaining levels. Weight was steady. Then they offered the high protein diet ad libitum and the subjects (who were told not to expect weight loss, this wasn't a weight loss study!) and they spontaneously reduced intake by ~440 cal/day and lost an average of 10.8 lbs in 12 weeks. As the study authors stated, the weight loss was fully explained by the reduction in caloric intake. I would also note that the insulin levels "spiked" and remained rather high for several hours throughout the day for all three dietary interventions.
I'm not sure what sort of delayed effect of insulin I'm supposed to be waiting for here.....
So ... to all still clinging to the last vestiges of insulin theory, I implore you. Try to forget everything you've "learned" from a certain guru. Look at the data objectively.
We've come full circle from James/Me addressing the error of extrapolating short term insulin action to long term accumulation of fat, to Todd now inferring some long term action of insulin we're somehow missing in these studies only looking at a snapshot of fasting insulin levels.
Embrace the tautology!!! It's not all that interesting, I know. But it tells us a lot.
(Not directed at Todd) Let the why-ning begin!!