For one, a high-carb diet will also shorten your life, the researchers found—but the fundamental point is about the type of carbs you eat. Eat carbs that are rich in sugars, such as white rice or bread, and you'll also reduce your chance of a long and healthy life.
And where you get your protein from also matters; someone who gets it exclusively from meat won't live as long as someone else who relies more on vegetables (also a carb, by the way), nuts and whole-grain foods, the researchers found. People whose diet is 50 per cent carbs (and presumably healthy carbs) isn't affected one way or the other.
Now to the details. Researchers from the Brigham and Women's Hospital in Boston analysed data collected from the Atherosclerosis Risk in Communities (ARIC) study, which had tracked the health and diets of 15,428 people through a series of questionnaires (first alert).
Dig deeper and those on a low-carb diet were also more likely to be overweight, smoke cigarettes and have diabetes, and they were getting more of their protein from animal fats rather than vegetable fats. Not surprisingly, there were more deaths in this group over the 25 years of the study than from other groups.
The researchers said they had factored in these risk factors, but admitted that they relied on just two questionnaires, spaced six years apart, and these are known to be hopelessly unreliable—because people lie or forget or exaggerate.
So the real take-home: don't read the headlines, dig deeper, ask questions.
(Source: The Lancet, 2018; http://dx.doi.org/10.1016/S2468-2667(18)30135-X)