I've been fasting for 2 weeks now.
My longest was 26 hours, but I also did 24, 20, 19, 18, 17, 16... I've been trying to just fit it in with my life, which isn't always that easy!
I'm having some difficulty with fasts that go through the work day. If I break the fast at lunch I'm good, but the afternoon gets my brain going a little squirrely. I don't know how to describe it exactly - I'm not exhausted, just feel "off" in the head.
Feels like my best bet is actually 24h fasts that go lunch to lunch. But then I miss the family dinner "ceremony" so I'm still figuring this out.
I've been trying to keep on the exercise, and mostly that's been great! I've been doing my running/biking at a moderate pace if it's later into a fast, but if it's near the start I use it as a way to deplete glycogen sooner.
It's a complete mindset shift - when you're a runner/cyclist, you're always told to eat to train, then get home and eat to recover.
I've been most surprised by the cycling. It's crazy to me that I can go for 2, 2.5h on the bike without bonking. Just have to watch the intensity - when I'm actually training for something, I will have to figure that part out. Presumably I'll do my cycling during the non-fasted state and consume stuff on the bike.
So far... nothing.
Me Enjoying my Feasting Period
Now I have to assume that the "Insulin Resistance" problem takes more than a couple weeks to resolve. But I need to eat better - in the eating windows I've been feasting like Friar Tuck.
I also haven't been very good at reducing refined carbs, one of Dr. Jason Fung's pillars of health and lowering insulin levels.
"Reduce intake of refined grains and sugars, moderate protein consumption, and increase natural fats"
... sounds good, but I whip up some guacamole (natural fats!) and then eat it with... chips (refined grain). Because it's delicious that way. Dr Fung suggests condiments mostly (olive oil, butter, etc) - but they have to go on something. Dairy fat is the one that's easy (mmm cheese!), I guess I can feast on nuts and avocados a bit... I should really google some high fat recipes.
They talk about "periodization" of nutrition, and a lot about "low carb" states!
The long and short of it - in non-competition phases when your intensity isn't as high, there are times you'd want to train in a low/no-carb state.
"Not throwing carbohydrates in massive quantities at every training session" ... which he says is the "old advice". I think it's also the advice every manufacturer of sports drinks and gels wants you to take!
In the "Build" phase - his suggestion is to have a high intensity session in the evening, recover with high fat / low carb, sleep, then wake up the next morning and do a lower intensity session in a low-carb state.
He also stresses the need for carbs for intensity - this stands to reason.
"How often should you be training with low carbohydrates?"
No more than 2 times a week, in the "Build" phase.
Etc! It's a great listen.
He doesn't address fasting specifically, and his focus is on getting the best cycling results, not losing weight.
I haven't been "racing" and I'm certainly not an "elite athlete" so my focus right now is on weight loss, not on training adaptations.
Glad to hear though that while I'm meeting my weight loss goals, I'm not totally out to lunch on the endurance training side. Low/no carb states aren't incompatible with training. It will just be a question of finding the right balance.
I recently read The Obesity Code by Dr. Jason Fung. He makes a compelling case that the old advice "Eat less, Exercise more" is ineffective. And this is backed up by studies showing almost nobody keeps off weight with that approach.
If you don't feel like reading an entire book (although it's great!), then check out this video... hits the key points.
The book is mostly not about fasting - he actually doesn't bring it up until the very end. Instead it explores the advice we've generally been given, and the science of why we are fat.
His claim is that the root of the problem is hormonal, and primarily insulin.
Boiling it down: we are fat because of what we eat and when.
The What: Sugar and refined carbs. These create elevated insulin responses that ultimately lead to reduced insulin sensitivity, which result in more insulin, which makes us fat. He also takes aim at artificial sweeteners, which provoke an insulin response despite having no sugar in them (!).
The When: Snacking, snacking, snacking. We eat too much, and the advice to "graze" makes it even worse. Our bodies are flush with insulin, always, which just makes the body numb to it... which again leads to even more insulin, which makes us fat.
This is where fasting comes in. There are various approaches, but in all cases the idea is to reduce insulin for long periods of time by not introducing new glucose into the bloodstream, thus no insulin response. This in turn has been shown in studies to increase insulin sensitivity, which he argues is the cure for obesity.
My Weight, and How I Will Apply It
I was an outlier in 2014... and had a bit of swagger about it. I had lost weight and held it off for 10+ years. I did it through calorie reduction and exercise. And it was bloody hard.
I'm not anymore. I weigh 212lbs, vs the 235lbs I weighed at my peak - but I'm almost 30lbs above the 185lbs that I need to be "Normal" rather than "Overweight", and a good 40lbs above where I'd like to be.
Fasting - in the past I had done 16:8 - basically not eat except between noon and 8pm.
But I think the 24h/36h fasts he suggests sound like they may be more effective. Fast for 24h 2-3 times a week, rinse, repeat.
Dr. Fung is very clear that exercise is good for you - it has a lot of hormonal effects, including increased insulin sensitivity and reduced Cortisol (stress hormone).
However he is very down on the role it plays in weight loss. Burning calories via exercise is not the way you will lose weight.
He mentions exercising while fasted is a "good time" - but it sounds like he's mostly talking about gym rats (and he even references the Lean Gains guy).