I have always had high at rest metaolic rate due to which I typically dont gain weight with normal diet. As I have aged I have put on some weight, my cholesterol level has been off the chart. I am doing on and off fasting (24 to 48 hr) for a month. I am concerned that my body will permanently alter and slow down the in rest metabolic rate due to which I am concerned about gaining weight if I stop fasting.
This is from the complete guide to fasting: Jason Fung Md I recommend you read it.
“In fact, metabolism revs up, not down, during fasting. This makes sense from a survival standpoint. If we do not eat, our bodies use our stored energy as fuel so that we can find more food. Humans have not evolved to require three meals a day, every day.When food intake goes to zero (fasting), our body obviously cannot take BMR down to zero—we have to burn some calories just to stay alive. Instead, hormones allow the body to switch energy sources from food to body fat. After all, that is precisely why we carry body fat—to be used for food when no food is available. It’s not there for looks. By “feeding” on our own fat, we significantly increase the availability of “food,” and this is matched by an increase in energy expenditure.Studies demonstrate this phenomenon clearly. In one, fasting every other day for twenty-two days resulted in no measurable decrease in BMR. There was no starvation mode. Fat oxidation—fat burning—increased 58 percent, from 64 g/day to 101 g/day. Carbohydrate oxidation decreased 53 percent, from 175 zero (fasting), our body obviously cannot take BMR down to zero—we have to burn some calories just to stay alive. Instead, hormones allow the body to switch energy sources from food to body fat. After all, that is precisely why we carry body fat—to be used for food when no food is available. It’s not there for looks. By “feeding” on our own fat, we significantly increase the availability of “food,” and this is matched by an increase in energy expenditure.Studies demonstrate this phenomenon clearly. In one, fasting every other day for twenty-two days resulted in no measurable decrease in BMR. There was no starvation mode. Fat oxidation—fat burning—increased 58 percent, from 64 g/day to 101 g/day. Carbohydrate oxidation decreased 53 percent, from 175 g/day to 81 g/day. This means that the body has started to switch over from burning sugar to burning fat, with no overall drop in energy.In another study, four days of continuous fasting increased BMR by 12 percent. Levels of the neurotransmitter norepinephrine (also known as noradrenaline), which prepares the body for action, increased by 117 percent, keeping energy levels high. Fatty acids in the bloodstream increased over 370 percent as the body switched over from burning food to burning stored fats.Figure 3.1. During fasting, basal metabolism and exercise capacity are maintained.”
It can over time. The best way to avoid that, you to overeat by a bit on your non-fasting days. You might also need to change up your fasting schedule occassionally so your body doesn’t get accustomed.
You would need to point to a study that hints at this idea.
The only thing I can think of, comparably, was the Biggest Loser study – but that was much, much different.
Contestants did hours of cardio, barely ingested any calories, and abused diet pills – for months on end. Their rate of weight loss was — extremely reckless, as well.
24-48 hours is really not a long duration at all for an isolated fast.
I’d argue it’s more natural/ closer to our ancestors – who had feast and famine between hunts – than doing what most modern humans do – stuff their face every 5 hours.
As you lose weight, presumably, your BMR (basal metabolic rate) will decrease (this can vary as muscle mass burns more calories than fat mass). Same reason a 300 pound man typically eats a lot more than 150 pound man. It takes more calories just to maintain a larger bio-mass.
Yes. All the studies Fung gives is very short term. I did ADF for 6 months. Not only did my metabolism drop but I slow motility now.
The better study is one called MATADOR that showed a pattern of eating 14 days and dieting 14 days kept the metabolism from dropping. Thus fasting for 14 days is not likely to cause a problem. But you must eat normally for a substantial time afterward.
Does it matter? What’s worst? not fasting and getting fat and lazy forever (plenty of studies there, and real human examples!!), or fasting based on seeing everyone’s amazing results and enjoying your life healthily? In the absence of ‘science’, observe and critically think - make your own decision and test it yourself.
https://podcasts.apple.com/au/podcast/the-dr-gundry-podcast/id1434371530?i=1000594059562
Of course, I don’t disagree, but I’ll ask a question in the interest of discussion. These studies are normally going from fully fed to fully fasted when tracking days. If one fasts longer, clearly the results should be different and when we fast or keep ourselves at constant caloric deficit for weeks, this is yet a different situation. The first four days of any fast are significantly dependent on what the state is of the days leading up to the first day.
Does anyone have data on prolonged rolling fasts (weeks) or significant hormone tracking on longer extended fasts?
I’ve seen results that state that 12 weeks of straight caloric deficit (including fasting so maximal deficit) doesn’t loose as much as 12 weeks where a week of caloric surplus is mixed in at 3:1.
Let’s not make the mistake of thinking that a spike in a hormone on day 3 means that it remains spiked if you do a 21 day fast or that it spikes the same on a rolling fast. I’m not claiming I know what actually happens, just want to point out confirmation bias.
I hit a wall with EF as in not losing weight & hair loss etc. Not Losing weight was fustrating.
So, I gave EF a break totally for several months.
Now doing IF 18/6 or 19/5 shortening the eating window. Feel so much better & not as hungry. Losing weight & hair all good.
Have to not only listen to experts but also listen to your own results.