Thanks for posting this!

I've been trying to wrap my head around how the lipids systems work in our bodies. If that's you, too, check out Dr. Thomas Dayspring(a medical educator, also known as 'Dr. Lipid)'s work.

According to Dr. Sarah Hallberg (a diabetes researcher) carbohydrate overnutrition causes excess lipid production in the liver, leading, eventually to NAFL, but meanwhile, the liver is doing its best to get rid of the fat, exporting it as triglycerides and VLDL. So overnutrition (particularly carbs) eventually triggers metabolic syndrome - and obesity is a byproduct of that.

She's got TED talks, and an interesting interview with Dr. Peter Attia: https://peterattiamd.com/sarahhallberg/

I would *guess* the link between diet and aging has to do with, in today's environment of overnutrition, personal levels of carb tolerance, and, interestingly, we have triglycerides and VLDL levels as blood markers of someone having exceeded their limits.

As far as sirtuins, they're wrapped up, as you mention, with mTOR and AMPK. Fasting seems to trigger AMPK (which, like the rapalogues, suppresses mTOR) so an increase in apoptosis and so a general cleaning out of misfolded proteins and senescent cells.

Possibly interestingly, sulforaphane (an isothiocyanate from broccoli) has a similar effect on AMPK. Also, there's been recent work showing oleic acid (which is in olive oil) also activates SIRT1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7036014/

And fructose seems to be a special case, as it triggers the body to prepare for a period of water, food, or oxygen deprivation. Fat and water are stored, mitochondrial production shifts to glycolysis, But glycolysis produces pyruvates, which intracellularly are an issue. See: https://onlinelibrary.wiley.com/doi/full/10.1111/joim.12993

Disclaimer: I'm not bio-credentialed, just feeling my way along here. Do NOT take anything from me as gospel.