Category Archives: ketosis

Inzulinski indeks – merilo sproščanja inzulina po zaužiti hrani

SB00400 Glikemični indeksGlikemični indeks (GI) je dokaj uveljavljeno merilo obsega dviga krvnega sladkorja (i.e. glukoze) po zaužitju določenega živila. Precej obetaven koncept pa se v vsakdanjem življenju ni izkazal za uporabnega, saj ima kopico pomanjkljivosti, zna biti zavajujoč, ljudje pa tako zelo različno odgovarjamo na enake količine zaužitih OH, da so povprečja neuporabna za splošna priporočila. Vsekakor je bil eden izmed razlogov za razvoj merila GI kot pomoč pri svetovanju sladkornim bolnikom. Nekako naj bi preko poznavanja GI hrane lažje predvidevali svoje krvne nivoje glukoze in tako lažje obvladovali bolezen. Samo problem nastane ob dejstvu, da lahko tudi proteini brez OH povzročijo dvig inzulina, katerega poglavitna naloga je uravnavanje krvnega sladkorja. Prav tako pa obstajajo tudi živila, ki povzročajo prekomeren dvig inzulina glede na njihovo vsebnost OH. Zato je Holt s sodelavci [1] razvila merilo Inzulinski indeks hrane (FII-Food Insulin Index).

FII-Food Insulin Index

SB00400 Inzulinski indeksInzulinski indeks (FII) je merilo obsega sproščanja inzulina na zaužitje določene hrane. Temelji na merjenju inzulina po zaužitju 239 kCal (1000 kJ) določene hrane v primerjavi s sproščenim inzulinom po zaužitju 239 kCal belega kruha, v obdobju 3 ur. Torej večji kot je indeks določenega živila, več inzulina sprosti telo po njegovem zaužitju.

Glede na to, kako uporaben koncept je inzulinski indeks hrane, pomislite samo na množico sladkornih bolnikov, se presenetljivo malo govori o njem. Redke reference v znanstveni literaturi, sem pa tja kakšna omemba v blogu ali podcastu, vse pa najverjetneje zaradi majhnega števila živil, ki je bila do sedaj testirana za ta indeks. Poleg osnovnega članka [1] se da na spletu dokopati še do nedavne doktorske dizertacije [2], s pomočjo katere se je število testiranih hranil dvignilo iz 38 na 147.

V nadaljevanju predstavljam Inzulinski indeks živil (FI), razdeljenih v smiselne skupine. Količina vsakega živila je 239 kCal, prikazana pa je še razlika med Inzulinskim indeksom (FI) in glikemičnim indeksom (GI) živila. Zadnja metrika predstavlja, koliko glikemični indeks (GI) »podceni« izločanje inzulina.

Mlečni izdelki

Pri mlečnih izdelkih GI pričakovano podceni izločanje inzulina (FII) zaradi precejšnje vsebnosti beljakovin v mlečnih izdelkih. Nekako je to tudi logično iz evolucijskega vidika, saj sesalci mleko uživamo v obdobju največje rasti (dojenčki, mladiči), inzulin pa je anabolni hormon (pospešuje rast). V povprečju za celo skupino znaša razlika med FII in GI kar 20%!

Povprečni GI = 23%, povprečni FII = 43%.

SB00401 Mlecni izdelki

Kruh, žitarice, testenine

Skupina s precejšnjim deležem OH in relativno nizkim deležem proteinov in maščob, zato v povprečju GI dobro zadane FII, saj je razlika v povprečju zgolj 0,5%. Vseeno pa vrsta hrane, po kateri se inzulin sprošča v največjem obsegu.

Povprečni GI = 58%, povprečni FII = 57%.

SB00402 kruh žitarice testenine

Sadje, sadni sokovi, zelenjava, stročnice

Še ena skupina z veliko OH ter malo proteini in maščobami. GI zato dobra ocena za veliko sproščanje inzulina.

Povprečni GI = 47%, povprečni FII = 50%.

SB00403 sadje zelenjava stročnice

Meso in proteinski viri

Z beljakovinami ter maščobami bogata skupina, kar ob relativno nizkem deležu OH pomeni precejšnjo podcenitev sproščanja inzulina.

Povprečni GI = 13%, povprečni FII = 24%.

SB00404 meso proteinski viri

Pijače, slaščice, prigrizki, obroki, hitra hrana

Oz po domače junk food. Veliko OH, kar nekaj maščob in brez proteinov, GI pa dobro oceni obsežno sproščanje inzulina.

Povprečni GI = 45%, povprečni FII = 52%.

SB00405 pijače sladice prigrizki obroki

Maščobe in olja

Sicer samo olivno olje ter maslo, GI in FII pa pričakovano zelo nizka. Maščobe pač ne povzročajo sproščanja inzulina.

Povprečni GI = 2%, povprečni FII = 3%.

SB00406 maščobe olja

Vse skupine na eni sliki so na voljo tule. SB00407 skupaj

Na naslednji sliki pa so predstavljeni sortirani podatki glede na Inzulinski indeks. SB00408 skupaj sortirano

Še nekaj korelacij

V nadaljevanju je pa še nekaj grafkov, kjer sem skušal prikazati povezavo med Inzulinskim indeksom (FII) in Glikemičnim indeksom (GI), vsebnostjo OH, proteinov ter maščob. Pričakovano je najlepša povezava med FII in GI, med FII in vsebnostjo OH pa relativno slaba. Kar seveda nakazuje, da vsebnost OH ni nujno vedno dober indikator za sproščanje inzulina po obroku. Od preostalih dveh hranil pa je še nekako najboljša obratna korelacija med FII in maščobami, skladno s pričakovanji. Večji delež kot je maščob v neki hrani, manjša je vsebnost OH ter posledično nižja potreba po sproščanju inzulina.

SB00410 korelacije

Zaključek

Inzulinski indeks je seveda (vsaj na papirju) uporabnejše merilo kot glikemični indeks, katerega bi bilo smiselno preiskusiti še v kakšnih večjih prehranskih študijah. Zaenkrat je njegova največja omejitev po mojem mnenju odsotnost podatkov za večje število hranil, analiza inzulina v krvi pač ni poceni stvar, možni sponzorji študij (i.e. prehranska industrija) pa so vse prej kot zainteresirani za tovrstne podatke.

Na vsak način pa da inzulinski indeks zelo uporabne podatke za npr. bolnike s sladkorno boleznijo, metabolnim sindromom, ljudi ki se želijo prehranjevati s ketogeno dieto ali izgubiti telesno težo z Low-Carb prehrano. Lepo se sklada z npr. mnogimi poročanimi anekdotami, da ima kar nekaj ljudji kljub Low-Carb prehrani težave z izgubo telesne teže. Ob analizi njihovega jedilnika ter kasnejšemu črtanju oz. omejitvi mlečnih izdelkov, pa telesna teža ponovno začne padati in tako lažje dosežejo svojo optimalno telesno sestavo. Kot je razvidno iz inzulinskega indeksa, imajo mlečni izdelki precej večji vpliv na sproščanje inzulina, kot bi mogoče sklepali zgolj po njihovi vsebnosti OH. Nekaj podobnega velja tudi za meso ter ostala hranila, ki vsebujejo precejšen delež proteinov. Vsekakor pa velja priporočilo, da vkolikor je vaš cilj zmanjšanje oz. omejitev sproščanja inzulina, potem uživajte čim več hranil iz zgornjega dela naslednjega spiska.

SB004011 zaključek

Literatura:

  1. Holt SH1, Miller JC, Petocz P. An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods. Am J Clin Nutr. 1997 Nov;66(5):1264-76.
  2. Bell, Kirstine. Clinical Application of the Food Insulin Index to Diabetes Mellitus. PhD Doctorate. University of Sydney. School of Molecular and Microbial Bioscience. 14-May-2014
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My thoughts on ketosis for athletes

Ketosis was the topic that sparked the most objections when I described it as the “promise land” in my low carb journey. Responses ranged from anywhere between “you were not in ketosis” to “6 week adaptation period is not enough” and in-between-the-lines “you are a pussy”. Mainly this is also my fault, as I didn’t described my experience with ketosis in greater extend. Therefore the topic merits another blog post from my side.

The Art and Science of Low Carbohydrate Performance - Jeff Volek, Stephen PhinneySo for anyone not familiar to ketosis I would refer you to an excellent book The Art and Science of Low Carbohydrate Performance by Jeff Volek and Stephen Phinney or to (free) article by Phinney. Also, the entries for Ketogenic diet and Ketosis are fairly well written in Wikipedia.

The basic premise of the ketogenic approach to endurance training lies in the fact that by greatly reducing the amount of carbohydrates in diet the body is relying mostly on ketone bodies for muscle and brain fuel. Ketone bodies are produced from fatty acids, of which we have basically unlimited stores. Hence by not relying on glycogen stores for fuel, one could not experience the so feared bonking. When studying the topic in literature I was skeptical at first, but decided to give it a try nonetheless. The issue that bothered me the most was, why isn’t this approach more popular, if the benefits are quite substantial, as described in famous study by Phinney et al. Also, Peter Attia reported some favorable results at his blog that additionally convinced me to try it out.

Blood ketone measuring device - Abbott Precision Xtra

So with good hopes and armed with blood ketone meter (and that expensive testing strips!) I reduced my carbs to under 50 g per day and protein to about 120 g per day. Over the 6 week period I had average morning blood values of ketones around 1,2 – 1,5 mmol/L. (That goes for the first argument “you were not in ketosis”). I was in ketosis all right, but I was feeling miserable as hell. No motivation to train, always cold, difficulties to start even basic movements like going to the bathroom, and I had traumas before swimming sessions as I was freezing in the water! It was MISERY in capital letters. Especially because my performance dropped like a piece of stone to the bottom of the pool. Sure, I wasn’t fading on long workouts, but the power and pace were very low. Also in interval work or hill repeats I couldn’t find that extra low gear for maximum effort. It’s really hard to describe, as I know that I would not believe myself explaining it to me, if I wouldn’t have tried it! It just didn’t work for me and my style of training which involves quite a bit of interval training sessions per week. My body was basically starving, although I was consuming in the range of 6000 kCal per day. I’ve lost quite a bit of muscle and gained back some fat mass, because I misinterpreted my cravings for carbs with cravings for food.

This brings me to the comments like to “6 week adaptation period is not enough” and “you are a pussy for not sticking to it”. My reply would be, that 6 weeks in that state and training on average 3 hours per day, with approx. 5-6 interval training sessions per week, seemed like eternity! And I believe that 3 years of 2-3 hours per day endurance training raised my self-discipline and pain threshold to a level, that cannot be offset very easily.

Anyway, after trying the ketosis and observing the effects, I would now line with the opinion by Robb Wolf that he nicely conveys on his blog in 3 parts (part 1, part 2, part 3). Or if you want a more colorful and juicy read head over to Anthony Colpo’s blog for his thoughts (part 1, part 2).

My experience with ketosis and large volume endurance training

My experience with ketosis and large volume endurance training

So to summarize, I believe that ketosis, being an evolutionary feature that enabled us to survive the periods of famine, is not a good approach to enhance endurance training, if that training (or racing) requires any significant higher intensity periods. Long ultra-endurance events could be an exception, but for “normal” endurance events and for goals more ambitious as “just finishing”, I believe that ketosis isn’t optimal approach. The endurance training by itself is already stressful enough, so the additional cortisol release during ketosis might just have too many negative consequences (i.e. muscle wasting).

Also, one of the major motive to go into ketosis while training and / or racing  is reliance only on endogenous stores of fuel (i.e. fat stores). I have now raced two Ironmans on “train low race high” carb approach and on both occasions I haven’t had a slightest issue with energy intake. Being fat adapted enabled me to efficiently burn fat in such extend, that I can easily manage the required carb intake during 9h event and still perform at quite high intensities (i.e. under 3 hour marathon on both Ironmans). In Hawaii 2013 I was consuming approx. 45 g of carbs per hour, which is almost half less of what I used to, when I wasn’t fat adapted (81 g per hour in Hawaii 2012). Hence, the required intake of carbs while being fat adapted is very manageable and will rarely cause problems also in athletes with troublesome stomach. Ketosis therefore looses another highly regarded feature, that was so alluring on the first sight. After experimenting with quantities, the arguments of “unlimited body fuel supply” and “unnecessary fuel intake during races” aren’t so appealing anymore when you also factor diminished performance into equation!

All in all, the ketosis experiment was very valuable experience for me. Having read most of the scientific literature on ketosis and endurance training, surfing through numerous blogs, podcast and videos I must say, that reading cannot prepare you for the experience. You just have to try it to really see what ketosis is like.

That being said, I still plan to use ketogenic nutrition periodically when I finish competing and return to “normal living”, as there have been suggestions on its beneficial effects on general wellbeing. Especially the idea of periodic intermittent fasting is appealing to me, as I think that we are more adapted to irregular meal timing. If the composition of the meals is appropriate, of course!

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