Effects of consuming a high carbohydrate diet after eight weeks of exposure to a ketogenic diet

Thanks to Leon for finding this :)

Effects of consuming a high carbohydrate diet after eight weeks of exposure to a ketogenic diet

Basically they took two groups of rats and fed them (ad libitum) either a ketogenic diet (KD) or regular chow (CH) for 8 weeks.  Then they switched the diet of the KD group to CH (KD:CH) and continued to feed the rats for an additional 8 weeks.  As this was a rat study, the rats gained weight/grew for the entire 16 week duration of the study.  

The diets:  KD = 5% carb/15% protein/80% fat             CH = 60% carb/23% protein/17% fat

Now I'm not a rat, but I do find these results both interesting and a bit surprising.  Here are the graphics for caloric intake and weight:

caloric intake: 

Surprise #1:  The KD rats consumed pretty consistently fewer calories (although the difference is not noted with an * for statistical significance) for the first 8 weeks and yet gained consistently more weight.  I'm not sure if this difference was stat.sig. either, but it was mentioned in the results:

After 8 weeks of consuming a ketogenic diet, KD rats had increased adiposity and plasma leptin levels, and reduced insulin, as compared to CH controls. 

So much for the insulin-induced fat accumulation theory once again.  And so much for the metabolic advantage -- if anything, this demonstrates an advantage for the high carb diet.  But CS, doesn't this violate calorie balance?  Nope.   I'm sure there's a TEF or RMR change in the KD rats vs. the CH ones that would explain this seemingly nominal discrepancy.  Furthermore, the KD rats had significantly more epididymal fat (one type of visceral fat) than the CH rats.  Is this a good thing for a rat? .....

Surprise #2:  Initially after the switch, the KD rats didn't go on a soaring blood glucose fueled carb binge.  They actually reduced caloric intake significantly in the first week after the switch.  Presumably these animals had a bit of insulin resistance and blood coursing with postprandial glucose during this first week of the abrupt switch.  And yet this didn't send the rats into a carb frenzy.

After that "honeymoon", however, the KD:CH rats increased their caloric intake over the rats who just ate the regular chow diet the whole time.  This increase is consistent but does not become statistically significant until the last three weeks of the study.  Is this an overcompensation for metabolically "starving" for extended periods?

The hormone level results are totally antithetical to the whole insulin/fat accumulation theory.  KD rats had significantly higher leptin and lower insulin levels than the CH rats.  However this would predict lesser adipose accumulation in KD vs. CH right?  Not the case.  The leptin remained elevated for several weeks (4) following the switch for the KD's.  REPEAT:  lower insulin in KD correlated with increased adiposity (visceral at that).

From the discussion:

Whereas KD rats had significantly increased fat pad weights and plasma leptin levels as compared to CH rats, resuming the chow diet prevented a further increase in adiposity and leptin over time. Rats that consumed chow for the entirety of the study increased fat pad weight and leptin to resemble those of KD:CH rats by the end of the study. In addition, plasma insulin levels in KD:CH rats were not different from CH rats one week after returning to the chow diet, although it was significantly increased after 8 weeks of consuming chow after the ketogenic diet.

If I had my druthers:
1.  A third group kept on KD would have been interesting.
2.  Since they started to see this significance towards the end of the study, why not extend it a bit longer?

Personal aside:  Since I adopted my "cheating" method for LC weight loss and maintenance, this result is consistent with my experiences with going off LC.  In the past, I never "gave up" on LC, just strayed from the strict version of it and never got back to it.  I think there was a small honeymoon period whereby everything still fit and I didn't seem to gain so there was no big motivation to jump back gung ho on the wagon.  (I have no idea if the scale said so or not, but I'll go by size and ignore if there was any water fluctuation in there).  However after that brief period I didn't binge but the pounds sure piled back on fast.  The first 100 lb swing occurred in no more than 2 years but could have been mostly accomplished in one!  The second, in roughly the same time frame.  So fast that before I knew it I was back past where I started. I experienced weight losses in the wakes of some of my cheats during my 10 months or so of rapid losses.  I think because for long weekends or a few weeks (vacation) I probably ate less eating higher carb.  But now I'm a smarter cookie.  I know that I cannot continue like that because whatever the cause, I lose my sensitivity to how much I'm eating after a while of consistent carbs.