Previous attempts at "the low-carb thing" left him constantly hungry, but he decided to give keto a try anyway, intrigued by the high fat intake (as opposed to the Atkins diet, which focuses on protein). 
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Atkins is high fat as well - actually it says "eat as much fat as you like". 
While they are similar, keto is a more rigorous and detailed approach. 

Low carb is not only about losing weight and minimizing seizures for epileptics.  
Low carb is shown to reduce inflammation, improve lipid profile (against all main stream advice we have been given since the 70s), slow aging, minimize the amount of free radicals running in our bodies. 

As for not being constantly hungry: it has a simple explanation - it gets you off the insulin roller coaster. Once your body starts producing ketons you easily go 12h without food. If I had an avocado/egg/meat (or fish) meal I can go 24h without eating (no starving).

Labels: moderation: safe