[SketchySeaBeast]

That feels like the incorrect framing, the burden of proof is on the initial claim. That'd be like saying "I've heard online that leprechauns live on the moon. I haven't found published research on it, but I think science in this field is lagging behind personal telescopic experience. If there's evidence to the contrary let me know, but I've read it online a lot." and treating that like it's proof of moon leprechauns.

[al_borland]

It's not exactly the same, as there are studies, there just haven't been a lot yet, since a lot of the study around it is new, although fasting has been practiced for thousands of years. There is no money in fasting, so the number of organizations willing to fund the studies goes way down.

To put some numbers to it:

https://pmc.ncbi.nlm.nih.gov/articles/PMC10564080/

> Only five out of the 1304 studies on NAFLD involved IF.

Here is one that mentions there may be some efficacy to the idea and no harm.

https://pmc.ncbi.nlm.nih.gov/articles/PMC8958240/

> In conclusion, current evidence suggests that intermittent fasting in patients with NAFLD is a feasible, safe, and effective means for weight loss, with significant trends towards improvements in dyslipidemia and NAFLD as illustrated through non‐invasive testing (NIT).

If someone has NAFLD, they can either sit around and eat cake for 20 years waiting for the science, or they can try doing some fasting, which is very low risk (assuming they don't have other issues going on), and find out very quickly if it works for them. Sure, it's an n of 1 in that case, but who cares, if they are the test subject it only matters if it works on them.

I'd add to this that the carbs should be kept low and the diet having quality foods outside of the fasts. Eating aforementioned cake during a feeding window every day is going to leave a person miserable, burning muscle, and still leave the hormones all screwed up. Insulin needs to be controlled and lowered. Fasting does that quickly, but don't abuse it during your meals on a regular basis.

From what I've read elsewhere, fasting can help in the early stages to reverse it, but once real damage occurs that sticks around.

[nradov]

There may be some medical benefits to periodic fasting, especially for people with excess adipose tissue. But in terms of "no harm" the Memel et al paper you linked doesn't seem to mention anything about loss of lean muscle tissue. This can cause serious harm for some patients — especially older patients with the "skinny fat" body type — by leading to sarcopenia (higher musculoskeletal injury risk) and endocrine dysfunction (muscle is a glucose sink). Loss of muscle can be limited to an extent by doing resistance training and maintaining high protein intake during non-fasting periods. But overall there are still a lot of unknowns in this field.

[al_borland]

A lot of that would be covered under the “other issues” I mentioned. Obviously, consult with your doctor first.

In terms of muscle loss, from what I’ve read, muscle loss is more of an issue for low calorie carbohydrate based programs. When fasting there might be some muscle loss when at the very start, but then it tends to preserve muscle, and like you said, adequate protein intake and resistance training can mitigate that.

Those, like Peter Attia, who saw muscle loss from long term keto and fasting over several years, weren’t using fasting as a medical intervention. He was already metabolically healthy, but maintained a pretty extreme fasting protocol in an effort to gain longevity benefits, effectively experimenting on himself based on some results of early studies around the benefits of fasting for longevity.

The general theory now seems to be making the fasts much less frequent once healthy. Maybe only a couple times per year.

I’m sure this area of study will continue to evolve slowly.

[watwut]

Add also refeeding syndrome to the list of risks. It can also serve as trigger for eating disorder.

Long calories deficit can lead to permanent brain damage too. And heart damage.

[SketchySeaBeast]

From your chosen quote, it doesn't seem to indicate that fasting specifically changed things, but fasting being an "effective means for weight loss" was the bit that really mattered. I don't see anything to divorce the two - general weight loss and improvement to the FLI.

> Available evidence suggests that any form of caloric restriction may be beneficial and specific forms of IF should be tailored to the individual.

Also important to notice that once the liver is damaged it's not recommended to fast:

> Additionally, it is important we investigate the possible risks of fasting in patients with cirrhosis, which is currently not recommended.