Does A Low-Carb Diet Shorten Lifespan?

August 20, 2018

There has been a lot of buzz about a study that was recently published in The Lancet stating that low-carb diets have been shown to shorten lifespan. There were so many issues with the study, however, that many well-known health and nutrition experts debunked it, including my fave, Chris Kresser, who sent out his first-ever Tweetstorm about it. Here are the highlights:

1. The diets of the study participants were only assessed twice over a period of 25 years -- once at the start of the study and once 6 years later. Participants filled out questionnaires on their diets asking them how often they ate certain foods. Do you remember what you ate last week (let alone 6 years ago)? And what if someone changed their diet during the remaining 19 years of the study??

2. Those who ate the low-carb diet were also more likely to have a higher BMI, exercise less, smoke cigarettes and have diabetes. If that was the case, how do we know if they had a shorter lifespan because of their low-carb diet? What if it was because they smoked cigarettes or had diabetes? There's no way to know for sure.

3. It doesn't make any sense to say that the optimal diet for humans is 50-55% carbs. Different cultures eat very wide ranges of macronutrients (from the Inuit who eat 90% fat, to the Kitavans who eat 70% carbs), depending on where they live -- and all are relatively free from modern disease because they all eat high-QUALITY foods. Which brings me (or brought Chris Kresser) to the next point....

4. This study didn't look at food quality at all. The low-carb dieters in this study, in fact, were said to eat very few fruits and vegetables. A nutrient-dense low-carb diet would include a LOT of vegetables, so the study participants' diet couldn't have been very nutrient-dense. Which means it wasn't healthy.

They can't really ever DO a study to figure out which diet is the best for longevity because the subjects would have to be locked up for years with no external influences on their health -- and every morsel they ate would have to be recorded. Who would volunteer for that???

The media turns low-quality and/or biased research like this into attention-grabbing headlines like "Eating Pasta Could Save Your Life," so it's important to take every headline with a grain of salt. Or just focus on food quality and ignore the headlines altogether!