Thursday, 17 May 2012

Intermittent Fasting and Diurnal Cortisol

A new study that is the buzz in the media is about how restricting feeding to an 8 hour window ( during the afternoon-night phase ) prevents the progression of obesity on a diet that otherwise induces obesity in the same rodents if they are given Ad Lib access to the same food around the clock.

The intermittent fasting rodents consumed the same number of calories as the Ad Lib fed rodents yet remained much more slim. So yes, this proves a calorie is a calorie btw. /sarcasm

This has come at a time that I was thinking about something mentioned on itsthewooo's blog in the comments about diurnal cortisol. Actually, cortisol essentially makes you quite glucose intolerant, ( like melatonin ), and induces insulin resistance, so it is most likely not a good time to eat food when cortisol is high, like first thing in the morning or immediately after exercise.

This is the daily graph of diurnal cortisol for a normal healthy person. It might be slightly different for an obese person, but it quite clearly highlights the problem with eating food immediately after waking up, especially sugary cereal. You should ideally only be eating when cortisol is low, that means during the late afternoon and evening. Could this be one of the reasons that helped the rodents in the IF study above resist obesity? ( maybe not, since rodents are nocturnal animals by nature, it makes sense for them only to be eating during the night. )


  1. Very interesting, and naturally I agree :)
    Few people seem to have an appetite in the morning, and advice to eat early and fast in the evening is unnatural to our impulses as well as counter intuitive to our endocrinology.

    In the case of the rodents, I wonder if the picture is an accurate representation of hteir feeding pattern - did the rodents really eat their calories evenly over a 24 hr period? This would suggest the rodents simply were not ever sleeping a dedicated block of time. It may be that many of the problems observed in rodents fed a high fat diet might be that in rodents high fat diet leads to wakefulness because they are preoccupied with eating the novel fat food, so the rodents do not normally sleep during the day like they should. In other words, the metabolic abnormalities are not just from fat but primarily because the rodents are not sleeping normally, which is well known to EXPLODE the body.

    1. now, THERE'S an interesting idea.... i wonder if anyone has ever made a note of WHEN ad-libitum-eating mice get their intake?

  2. I never ate breakfast until CW got to me and I started to consume cereal. Nothing used to make me more nauseated than eating that sugary garbage in the morning. I couldn't even finish the bowl. Somehow I didn't think this was a sign that breakfast is bad for you, I thought it just took getting used to. LOL - brainwashing really works.

  3. dunno the feeding pattern of the ad-lib rodents the full text is behind a paywall :(, BUT yeh I doubt they are eating constantly throughout the day/night. However I think that if food is constantly under your nose, you tend to graze and nibble, that cant be good tbh, even humans do this.

    Im sure I tend to over produce cortisol slightly, rarely am I hungry in the morning, and even after exercise it takes about 2 hours for hunger to set in. If I eat immediately after exercise it just feels really fucked up. It makes me feel very stiff.

  4. Oh, I just groan when I read some of these IF studies, since I am not a rat and I IF was also a disaster for me when I got older and combined it with a desire to reduce calories. I say desire, since my overall amount of daily calories didn't really go down that much. Yes, a calorie is a calorie, but zig zag calories on alternative days led to disordered sleeping and nighttime eating. This is why I like Jack Kruse. Despite being mad, he was the only one with a plausible explanation as to why IF is bad for some, and he is the only one I know warning people about it.

  5. I did not start loosing weight continuously until I started skipping breakfast. Two tsp of coconut oil in the morning coffee gives me the energy needed to walk to work, run around for a couple of hours, and walk back home for lunch. Eggs and a salad is my typical lunch. When I do this, I consider it having nailed it until dinner. I am glad to learn the science behind what my experience has shown, eating early is just extra calories that are not needed, and lead me to weight gain. The eating window type of eating was popularized by the Fast5 diet. I did this several years ago and did loose weight. I could not maintain with the program and was for nauht.

  6. I've linked to this in the comments here:
    The eating window works for me, which is about the fatty liver and DM2 benefits rather than weightloss.
    What would happen if they switched the fattened rats to the IF diet?
    What would happen if they disordered light cues fr the IF rats, but kept them strict for the non-IF?
    Here's the fulltext of the study you posted about:
    Panda Salk IF trial