Friday, August 24, 2012

Carbs Past 6PM Reloaded: Circadian Shifts in Leptin and Ghrelin + Rising Adiponectin During the "Carb-Fast" Could Explain the Efficacy of Eating All Carbohydrates at Night

Image 1: Paul Bart (Kevin James) in Mall Cop (Columbia) probably would be better off weight- and health- wise without his Segway, which is by the way among the "50 Worst Gadgets of the Decade" in the Business Insider hall of shame from 2009 (Barret, Brian. 2009)
The SuppVersity was the first place you read about the how "Carbs past 6pm Will Make You Lean" (at least about the non-anecdotal scientific evidence) and for 99% of you, this will probably be the first time you read about the "follow up paper" on the original study, which was originally intended to induce a shift in the circadian pattern of leptin secretion in order to make use of its fat burning effects over night. Exactly this is the focus of a follow up paper that's soon going to be published in Nutrition, Metabolism & Cardiovascular Diseases (Sofer. 2012).

Israeli Police Diet Acadamy Reloaded!

Now the bad news is that the news are only partly new. In other words, the Israeli scientists only reevaluated the original data which was based on 63 overweight police officers who finished the original "don't eat carbs before dinner study."

And if that was not already enough, the complete hormonal profiles which had been collected on days 0, 7, 90 and 180 of the study period were only available for 39 of them.
Figure 1: 24h leptin profile before and after the intervention in the control (left) and experimental (right) group
(graph adapted from Sofer. 2012)
Still, the data in figure 1 does support the original hypothesis that the mechanism due to which the participant on the experimental diets (composition see figure 3 in "Carbohydrates Past 6PM Will Make You ... Lean!") lost ~2% more weight, and ~4% more body fat was in fact a shift in the circadian expression of leptin:
I suggest you go back to the original "Carbs past 6pm Will Make You Lean" post to read up on the details; unless you're a longstanding reader and this reminder is enough for you.
"On day 0 both groups demonstrated typical concave diurnal leptin curves, including a fall throughout the hours of 08:00-16:00, reaching a nadir at the afternoon and a rise from 16:00. On day 180, leptin curves were lower compared to day 0 in both groups. In the experimental group, the curve became more convex with a nadir only in the evening and not in the afternoon (figure 1, right). A significant difference was observed within the experimental group between day 0 and day 180 in the morning and in the evening (p = 0.023 and p = 0.021, respectively). For subjects in the experimental group that had complete data, the change in evening measurements from day 0 to day 180 was significant (p = 0.024). Using these data, the change in evening measurements was significantly greater than the afternoon and the noon change (p = 0.009 and p = 0.014, respectively). In the control group, a significant difference was observed between day 0 and day 180 at noon (p = 0.042). This result was also found for subjects with complete data (p = 0.045)." (Sofer. 2012)
What's also noteworthy is that the sparse information the scientists had on the ghrelin levels of their participants (believe it or not, but the nurse or whoever took the blood samples must have messed up, so that much of the data was lost) would suggests that the "post 6pm group" (=experimental group) were freaking hungry in the evening (see figure 1, right), but this was not the case, contrary to the subjects in the control group which had carbs from AM to PM, they did rather expose an "enhanced daytime satiety" an observation based on which Sofer et al. rigthly state that
"[...] the alteration in ghrelin’s peak from daylight hours to the evening just before dinner was another cause for the elevated daylight hour satiety, improved persistence in the weight loss process and better anthropometric outcomes that were reported [16]." (Sofer. 2012)
Next to with the circadian shifts in leptin and ghrelin levels, the pronounced increase in adiponectin (see figure 2), a reliable marker for an improved glucose tolerance, the "carb binges" which as you will probably remember included desserts such as ice-cream and co (see figure 3 in "Carbohydrates Past 6PM Will Make You ... Lean!"), probably is the third pillar of the superiority of the past-6PM carb regimen over the conventional "eat small amounts of carbs all day" approach  the control group was following.
Figure 1: 24h Adiponectin profile before and after the intervention in the control (left) and experimental (right) group
(graph adapted from Sofer. 2012)
In conjunction those three made the "impossible possible": Eat all instead of no carbs past 6PM and lose weight! Now the unfortunate truth is that this works well for people with compromised insulin sensitivity and anywhere between 15-20% body fat to shed before they approach the level of leanness (<20%) most of you probably started out with, whether it will work similarly well for significantly leaner, physically active individuals, on the other hand, remains to be seen.
Video 1: I don't want to be a spoil, but the weight loss program of the Stadtwerke Cologne which works by simply skipping dinner (!) and without any caloric restriction got some series attention here in Germany. Why? Well, it simply works... so what does this tell you? Maybe it's more about helping AMPK come to it's own, instead of stuffing yourself with readily available energy 24/7, than about exact timing or meticulously calculating macro compositions?
(click here to watch Quarks & Co.)
Bottom line: Irrespective of my all doubts about the applicability of the very same diet principle in a context, where the goal is to get really ripped and not simply non-obese, the study at hand (and I am referring to the whole experiment, here not just the last paper) does confirm that there is more to dietary success than calories in vs. calories out that having breakfast like a king is not a necessity (nuts + coffee, which was the standard breakfast in the experimental group, or nothing, which is Adelfo Cerame's standard breakfast, work just as well) and that the influence of circadian rhythms goes far beyond our sleep-cycles... which reminds me that I'll do my very best to get into more details on that in the coming episode III of the SuppVersity Circadian Rhythm Series on Sunday. Until then, try not to lose the beat ;-)

  • Barret, Brian. The 50 Worst Gadgets Of The Decade. Business Insider. Dec 31, 2009. < > retrieved on Aug 24, 2012.
  • Sofer S, Eliraz A, Kaplan S, Voet H, Fink G, Kima T, Madar Z. Changes in daily leptin, ghrelin and adiponectin profiles following a diet with carbohydrates eaten at dinner in obese subjects. Nutr Metab Cardiovasc Dis. 2012 Aug 14.