Inductivist

This new meta-analysis (more than 430,000 participants) addresses the question, Does it matter whether you eat a lot of carbs?

The researchers found a U-shaped curve: people were most likely to die if their diets were carb-heavy, or if they ate mostly fats and proteins. The subjects with the lowest odds of dying ate 50-55% of their calories in carb form.

The source of the macronutrients also matters. Mortality goes up if you eat fewer carbs but more of the fats and proteins come from animals; the risk falls as the fats/proteins are plant-based.

So, the story here is pretty conventional: carbs are good at moderate levels, while more fats and proteins ought to come from plants.

Typical of even medical research, the authors do not stress the possibility that people with genes that make you live to a ripe old age also eat more plant-based food. We know from research that high conscientiousness, which is highly influenced by genes, is associated with a long life. Good genes might: 1) motivate you to closely follow medical advice, and 2) extend your life. What you eat might not make any difference.

If that possibility sounds depressing because you can't switch out your bad genes, well I ain't here to make you feel good.  

UPDATE: I should let you know that my diet ranges from minimal carbs to low carbs depending on my level of discipline (lots of carbs makes me feel lousy, and I put on weight), so I have no bias in favor of the results of this study.