Typically on keto, you don't think about food at all, except when it is meal time. I've done both, and while PSMF does produce faster fat loss, the loss is not proportional to the reduction in calories. So (as an example) on a 1400 cal keto diet, you might lose 2lb a week, on a 700 cal PSMF, you might lose 3lb a week. More @Wikipedia
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