From Lyle: "Seriously, one of the most staggeringly 'brilliant' comments I read one time in a review paper was to the effect of "While we don't know what the ideal diet for the treatment of obesity is, it will most likely contain adequate protein, sufficient dietary fat, and emphasize fruits and vegetables."
Seriously, 3 decades and 10 billion dollars worth of nutritional research and they came up with what my grandmother knew 50 years ago. I mean duh.
Keto and Zone diets force people to get sufficient protein and fatty acids (and hopefully EFA's).
They also control hunger better. Meaning better compliance and calorie control. Both of which are crucial aspects of a diet. In that sense (hunger/calorie control), lowered carbs may very well be considered to have a 'metabolic advantage'. And one that makes such diets very beneficial from a fat/weight loss standpoint.
But in terms of causing significantly greater fat loss/less muscle loss at a given calorie level, the data just doesn't seem to be there. Not in the research, not in the real world. Not assuming the person is getting enough protein and EFA's in the first place. Basically, that's the issue in a lot of studies. Take someone with a crap diet (usually too little protein) to begin with, and a keto diet will be superior. Ketosis is VERY protein sparing if your protein intake is inadequate to begin with (many studies give 50 grams of protein or so while dieting). Assuming protein intake is adquate to begin with (at least 1.5 g/kg bodyweight), ketosis doesn't appear to have much of an impact.
And don't get me wrong, I really wanted it to be true, I really wanted such diets to cause greater fat loss and spare muscle better. I really did. This is just one of those cases where I don't think the research/real worl results support the idea that they do.
Basically, the way I see it you have to first:
1. Meet certain requirements: caloric deficit, protein, EFA's. That's required of any diet, no matter the interpretation.
2. Figure out the rest of the diet dependent on the person. If they are active, have decent insulin sensitivity, and enjoy eating lower GI carbs, a moderate to higher carb diet will probably be sufficient. Something like 50/25/25 or 40/30/30. If they are very inactive, highly insulin resistant and/or simply won't remove the high GI crap from their diet, reducing carbs further or removing them competely may be the only workeable approach to get calories/hunger under control.
Basically, there's what's required (deficit, protein, EFA's) and there's what's optional (everything else). What's required isn't up to debate: it applies to everyone. What's optional depends on the needs of the person.
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