Fasting places stress on the body, which in turn requires a response of more cortisol secretion. This quote is from the link below: During periods of increased stress, “the immune cells are being bathed in molecules which are essentially telling them to stop fighting,” according to Dr. Esther Sternberg (20). These molecules, namely cortisol, suppress the immune system and inflammatory pathways, rendering the body more susceptible to disease.

http://dujs.dartmouth.edu/2011/02/the-physiology-of-stress-cortisol-and-the-hypothalamic-pituitary-adrenal-axis/#.V7fCR6J0l1

I too came down with a flu for first time in years after starting 5:2. Interesting for me though that my flu developed after I’d experimented with one week of ADF, which puts even more stress on the body. What I’ve learned from the experience is that I need to be vigilant about managing stress caused by other aspects of life, while I’m living this WOL. This means ensuring I get quality sleep, not just the number of hours, but also consistent sleep wake rhythm. I also have to heed my time limitations and scheduling, allow myself ‘time out’ breaks to enable me to devote time to relaxing. Being more conscious of what I eat also plays a part since sugar is one substance that is directly related to lowering immune function. The week leading to the flu I developed, I’d been regularly indulging in home made sweet treats that I’d created using unrefined sugars such as coconut sugar, rice malt and xylitol. Nonetheless, those were still sugars!

Haven’t experienced more colds since fasting. After a viral infection in 2006 I now have colds which last a very long time, typically a month or more. Fasting does not seem to have made any difference.
Have you heard of the old saying “Feed a cold and starve a fever” ? Most people interpret this as ADVICE, the need to eat plenty of food if you have a cold and not eat at all if you have a fever. But consider that it may instead be interpreted as a WARNING, i.e. “If you feed a cold it may turn into a fever and you will have to starve it out.” Food for thought – pun intended.

I have had several colds during the past month but only indirectly because of fasting. Fasting helped me feel so much better that I signed up for classes at the University and came into contact with lots more viruses. I just carry on as usual. A cold is an inconvenience not a reason to stop your life, although my son seems to think it is. But there has actually been research that shows that men do suffer more from colds – Man Flu apparently has a biological basis!

I also keep fasting during a cold because I would feel worse if I didn’t. Digesting takes energy away from that available for activity or for healing. I only eat when I don’t have anything else to do. But I always eat well, meeting nutrient needs even on fast days including at least five different fruit or veg. Longer fasts would probably be a bad idea.

Hi @fatrabbit. Manflu definitely has a biological basis – see this really “helpful” website for more! (And a good laugh too.0

Just an update on my experiences with colds. As I mentioned in earlier post, the first 3.5 years I was fasting twice a week and experienced more colds. The last two years I increased my calories to 700 on my fasting days from the 600(I’m 6’2″ and 200lbs, so a bit bigger than average) anyway, my colds have dropped substantially. (It also may be related to being much more careful when flying…(not touching the magazines, tray tables and seats backs, disinfecting hands often, directing fresh air over face)). I became mostly vegetarian at about the same time I started the fasting and feel my colds are usually much shorter duration and/or less severe when I was getting them frequently. I can’t say for sure if it was the fasting or vegetarian diet but I don’t fear colds as much and do believe my immune system is generally stronger than it use to be. Best of luck to all!!