For the past 18 months I have often incorporated fasting into my week. It was brought to my awareness along with all the other ‘primal‘ leanings like avoiding lots of grains and high intensity training. The idea is that we are conditioned for periods of going without a meal from the days when the antelope escaped our best efforts.
Not only can we cope, it is believed to be beneficial in terms of giving your gut a time-out, and mixing up our hormones to our advantage: for example, working out in a fasted state promotes higher levels of growth hormones. It also helps us open up those fat metabolism pathways that are desensitised by our constant supply of carbohydrates (less so if you eat primal /paleo). Studies on rats in the 1930’s showed that their lifespan was significantly increased if their calorie intake was restricted. Of course, long term fasting or calorie restriction will result in decreased metabolism to match the dwindling supply and reserves, so an intermittent approach is the best bet for healthy but fully active living.
I read another interesting piece today on calorie restriction that expanded into the main topic of protein restriction (Protein Cycling Diet by Dr. Rob Mignery: link was found in The Four Hour Body by Tim Ferriss, which I shall discuss in the near future). It appears the life-enhancing effects of calorie restriction may be primarily due to autophagy: a process that can be triggered by protein restriction alone.
Autophagy is a process whereby the cells recycle old proteins in the absence of a sufficient supply. They portion-off waste /old /faulty material for destruction in order to reuse the building blocks. This deleting and defragmenting, for want of a computer analogy, stops the accumulation of old wasteful files that could result in a system crash. There is interesting discussion in the piece in relation to Alzheimer’s and Huntington’s disease (which prompted the writer’s study into the matter).
At any rate, one can still induce this autophagy by reducing protein for a period but maintain calorie intake, if desired, using no-protein foods like leafy vegetables, cassava, butter. This could be handy for me to keep in mind if I run into energy issues on my fast day, but I find it refreshing to forget about food and eating altogther.
I have gone 36hrs on only water a few times in the past year but typically just fast from dinner one night until dinner the next (24hrs). It’s not really been an issue as my calories are mainly derived from fat anyway so I don’t suffer mad feelings of hunger from having a massive carb supply shut off. Pavlovian stomach rumbles at meal times are small and short. If I am sedentary then I may feel a bit colder, and if active, less able to go all-out, but even for a highly active person that can be sacrificed for one day a week. Some other days I naturally fall into an Intermittent Fast: eating two meals in a 6-7 hour window. This still gives the gut a good 16 hour break and may still invoke a few hours of autophagy.
My only query with the study piece is the focus on a minimal protein requirement of only around 25g /day. As someone who strives for a high-level of 80-100g /day due to my training goals and exercise levels, I would have liked some expanded insight into this area. There is brief consensus that protein cycling is unnecessary in young people or those with athletic ambition, but any bearing on the figures would be nice.
Have you ever tried some regular fasting or calorie restriction?
* anything vaguely relating to science, or something that should have a source is in the linked articles somewhere.