It’s January, which means there’s still time to curb your existential dread about the passing of time with a few resolutions. Why not try a new diet? You could go Mediterranean, vegan, DASH — or you could just eat bacon and eggs and butter for the rest of the year. Perhaps you’ve heard of this bacon-based weight-loss plan: It’s called the ketogenic diet. And while it’s not without its critics, over the last few years “keto” has attracted throngs of devout followers who bless the diet for its fat-torching properties, claiming immense weight loss while maintaining energy and fullness. Keto...