Thanks mccoy, Mechanism & Sibiriak for sharing great info/papers - pleasure to read through. Particularly want to dig into the linked chemotherapy paper more, as it dicusses glycerol a lot.
Just to add to what mccoy said about the dose used by Valter Longo in their Prolon fast mimicking diet. Whilst the nutritional info mentions 20 calories per serving, on the actual bottles (which I've only seen recently) the serving size varies based on bodyweight. Essentially they have drawn little notches on the bottle, with the weight next to them. So you'd use as much of the bottle as gets it down to the applicable notch. For a 240lb person it's over 75% of the 118ml bottle.
Fortunately, we can reverse engineer the glycerol quantity because the bottle also says "formulated to provide 50 calories per 100 lb body weight". As mccoy says, there's 4 calories per gram of carbohydrates, so that's 50/4 = 12.5g of glycerol per 100lbs body weight. I made a simple calculator on this page, where you can type your weight and it outputs the amount of glycerine for each of days 2-5.
Then, and its nit picking, there's potentially an extra ~1g to 1.5g of glycerol per 6 calorie algae oil packet (which has glycerine added), added on days 1 & 5.
Side note, thought it was interesting to see "inulin", a plant based fiber source, as a primary ingredient on their choco crisp bar. Presumably to increase satiety and (possibly) decrease glucose spike? Will be curious to learn what other "tricks" they've used when formulating the diet.