Study: Low-Carb and Low-Fat Diets Are Not Associated with Increased Death; Unhealthy Food Choices Within These Diets Are

The findings of a study published in JAMA Internal Medicine show that low-carb and low-fat diets are not problematic in and of themselves – instead, the unhealthy food choices people make on those diets is linked with a higher rate of mortality.

In this prospective cohort study, researchers assessed 37,233 adults from the US National Health and Nutrition Examination Survey, which took place between 1999 and 2014. The population of interest were all 20 years of age and older. The researchers looked at unhealthy, and healthy low-carb-diet and low-fat diet scores based on both percentage of energy as a total as well as subtypes of carbs, fat, and protein. The primary outcome was defined as all-cause mortality, from baseline through December 2015. The researchers analyzed the data from July 5 to August 27, 2019.

According to the study results, low-carb-diet and low-fat-diet scores were not associated with total mortality. They researchers observed in multivariable-adjusted hazard ratios for total mortality per 20-percentile increase in dietary scores were 1.07 (95% CI, 1.02 to 1.11) for unhealthy low-carbohydrate-diet score, 0.91 (95% CI, 0.87 to 0.95) for healthy low-carbohydrate-diet score, 1.06 (95% CI, 1.01 to 1.12) for unhealthy low-fat-diet score, and 0.89 (95% CI, 0.85 to 0.93) for healthy low-fat-diet score. They found that these associations remained similar in the stratification and sensitivity analyses.

The research authors wrote in the conclusion that: “In this study, overall low-carb-diet and low-fat-diet scores were not associated with total mortality. Unhealthy low-carb-diet and low-fat-diet scores were associated with higher total mortality, whereas healthy low-carb-diet and low-fat-diet scores were associated with lower total mortality.”

They added that: “These findings suggest that the associations of low-carb and low-fat diets with mortality may depend on the quality and food sources of macronutrients.”