It’s a fact that when you exercise, the positive changes that happen to your body – increased muscle, fitness, lung capacity etc – do not occur during that process. They occur afterwards during sleep, resting and through eating the right foods. This too, it seems, is the way things work for fasting. Yes, when you fast your glycogen gets depleted, you dump water and your body start to eat its fat. You do see your weight drop. Autophagy and (later) apoptosis occur. However, these are only part of the process – the body stripping out the damaged and the useless, burning up excess fuel – and to complete it fasting must be complemented with ‘feasting’ and sleep.
I’ve noticed my weight going down a lot during fasting then coming up again during refeeding, but every time my weight has been steadily declining overall. This is all good, but I noticed that where the fat was disappearing I had loose skin and that the weight returned to the same place. Then real changes occurred with sleep that was unusual for me: for example snoozing for an hour during the day, then flaking out for nine hours in the night. This has happened a few times during refeeding and, each time, I found that my weight had stabilized at a lower level, fat had melted away and my skin had tightened up.
Now for some negative effects: The worst day of fasting each week is always the first. I feel tired and often cold. I reckon it’s because on that day I’m making the changeover from the calories I’d been eating to fat burning again. This doesn’t particularly slow down a gym session in the morning or stop me writing during the day. I don’t feel particularly hungry either, probably because, having done this for so many weeks, I’ve accepted on some unconscious level that I am simply not going to eat on that day. On the following day the cold and lethargy go away and I don’t feel hungry then either. The hunger only returns when I actually start eating again.
Another noticeable negative effect has been an increase in anxiety. This would probably not be a problem if you are not prone to it, but I have been for a number of years now. It’s been said, wrongly, that your body will slow down and go into starvation mode whereby it tries to burn less and hang onto more. During dieting, and perhaps towards the end of a lengthy fast for someone not carrying piles of fat, this may be the case. However, during intermittent fasting the body does not get the chance to do this. The metabolism actually speeds up by dint of adrenaline and cortisol. And this of course can lead to increased anxiety.
Oddly, I have only experienced this in a way I rarely experienced while suffering from it long term. I don’t consciously notice it as I go about my daily routines, but do when I relax. Then I get a burning sensation mostly in my arms, but also elsewhere. My understanding of this is that it is the end of anxiety. The body fights for its own preservation by drawing the blood in around the major organs, when you finally relax, the blood returns to your extremities and hence this sensation. There are other effects too of this process, but they are not so bad that I am tempted to give up – the weight loss and other positive effects far outweigh them.