I have tried fasting in the past, (whilst eating paleo) but I just cannot make it beyond 4 or 5 hours without getting symptoms of low blood sugar - grumpiness, tiredness and the like (this is an especially awful experience for my kids). Could there be an underlying reason for this and how should I proceed, if at all??
It's interesting that you say you can't make it beyond 4-5 hours, since apparantly it's just after this (around 6 hours) that apparantly fasting becomes easy (certainly true to my experience). This is when your body moves from the post-prandial stage (after eating), realises there's no food about and so stops demanding a top-up and starts simply burning it's own stores (with lypolysis increasing throughout the fasting period. It's possible therefore, that you simply need to break this wall and then you'll be fine fasting after that.
In my own experience, there are some days/weeks when I can't fast at all and others when it's easy as anything. There doesn't seem to be any easily discernible pattern to this, although amounts eaten and stored previously would be an obvious one, as would exercise done recently. If I've not slept properly, then fasting often becomes impossible.
What do you eat when you're not fasting? If you're eating a decent amount of carb on your paleo diet, sufficient to be running your metabolism on glucose, then fasting will necessarily be somewhat harder, since you'll be switching from a glucose-based to a fat-based metabolism and keto-adapting takes a while. If you're eating a fully low carb diet then you shouldn't have 'low blood sugar' at all, in that you should mostly be fuelled by fatty acids, not sugar. The same will apply if your diet is quite heavily protein based, since above 25% of calories, it will start to depress your fat-metabolism and again you'll be fuelling yourself from glucose produced from the protein. It'll also raise insulin more and so lock the fat that you want to be burning during your fast.
One possible problem is that your body is simply not releasing its stored fat, for any of a number of reasons, I remember reading a study showing that in overweight individuals (not that I'm suggesting you're overweight!) they were less able to access their stored fat than lean ones (who knows which way round causation runs), perhaps it's due to higher insulin.
I'm interested to how this 4-5 hour limit applies in practise though. If you eat dinner a few hours before bed (say 3) then you'll have been fasting around 11 hours or so by the time you wake up... would you always need to eat breakfast first thing, without extending the fast? I always include sleeping time in my intermittent fasts, both because it seems like the best time for the body to focus on repair etc and also because I rarely want food just before or just after sleep.
Unless you have been diagnosed with hypoglycemia (which requires 3 things: symptoms of hypoglycemia, concurrent low plasma glucose concentration[fingerstick blood sugar] and immediate relief of symptoms when plasma glucose level is raised), it is quite doubtful that you do, in fact, have low blood sugar.
Now, I'm speculating, but it seems that perhaps you're at the cusp between glucose and fat metabolism, and this is period is definitely something you want to push through (i drink water or black coffee) if the goal is fat loss. There could be a component of social/physiological conditioning in there as well...remember that "true" hypoglycemia may have accompanying symptoms such as confusion, blurry vision, headache and heart palpitations.
You're not alone! The symptoms you describe are common for many getting into intermittent fasting...they do pass. It does get easier.
If you're truly concerned, seek appropriate medical care/testing. Otherwise, stick with it and it'll get easier; it's worth it.
In a nutshell - you should prepare the body, metabolically speaking, by low carbing (so paleo, but no fruit or starches) for at least 2 - 3 days, depending on how you react to that. This preparation switches over to fat metabolism/ketosis - which is where you're heading with a fast. If you still encounter problems try slugging down a tablespoon of coconut oil.
The above is supported by my own experience, not just research.
Try this approach before assuming you're a medical "case".
I'm hypoglycemia and currently breastfeeding my seven month old daughter. I've never fasted before. I'm quite religious and believe in God an all he's done for me, my family, my life. I feel he's telling me its time to put actions behind my faith. He sent me a word through someone close to me. Im concerned because i have low blood sugar and are a little concerned that fastinf for three days will cause me health issues and could also dry up my milk supply. Any suggestions?
If you don't have hypoglycemia as mentioned in the other posts, and you're just having loads of cravings you can try two things to get you over it:
a) extra virgin coconut oil. Start with just a teaspoon or two and work your way up. Yes, you can consume it while doing IF, as the point of the IF is to fix insulin sensitivity. The MCTs which are about half of the contents of coconut oil are easily converted to ketones, and are not processed the way other fats are, so it can kick start ketosis and get you adapted to burning fat instead of glucose.
b) Take a 1/8 to 1/4 teaspoon of L-Glutamine. It's an amino acid that can cross the blood brain barrier and shut down sugar cravings, as those parts of the brain can use it for energy.
I've also heard on here that alpha-lipoic-acid can help too, but I've not used it in this way.