Keto= no carbs (must be in state of ketosis in which fat is your fuel)
Atkins= low carbs
both shitty
from both 30% of the "loss" is from muscle
well on Atkins diet you can enter into and out of ketosis quite a bit. so the two are one in the same really.
a zero starch diet is not "shittty". in fact its very healthy and reverse allot of metabolic disorders. its very 'shitty' for anabolism, true, but for fat loss in obese individuals its very effective.
one thing people don't realize is that 'ketosis' is not some magical fat loss state. one ,meal containing zero starch and some meat protein will alter your metabolic hormones to dictate pretty much entire body fat metabolism. switching into 'ketosis' spares another 20 or so g of glucose, but other than that it has no benefit (besides psychology) over a simple low carb diet. a zero starch diet with high veggies intake is healthier and more efficient at burning fat than a similar diet without the veggies. but many people don't have the mental fortitude to diet on low carbs unless they are in ketosis.