Data regarding the dietary habits of tens of thousands of adults in the United States suggest that those who follow healthful low fat and low carb diets have a lower overall death risk.
“Diet plays an important role in […] public health, and suboptimal diet is estimated as the first leading cause of death and the third leading cause of disability-adjusted life-years lost in the [U.S.],” write Dr. Zhilei Shan — from the Harvard T. H. Chan School of Public Health in Boston, MA — and colleagues in their new study paper.
Their findings now appear in the journal JAMA Internal Medicine.
In their research, Dr. Shan and the team analyzed the data of more than 37,000 people to determine whether or not there were any associations between different diet types and mortality.
More specifically, the investigators wanted to find out if different types of low fat and low carb diet are associated with total mortality.
Although there have been several studies into the links between diet and death risk, the researchers note that — to their knowledge — none have looked specifically at how low carb and low-fat diets of different qualities may fit into the equation.
“Consumption of carbohydrates from refined grains and added sugars have been adversely associated with health outcomes, whereas consumption of carbohydrates from whole grains, nonstarchy vegetables, and whole fruits appears to be beneficial,” explains the study authors.
“Likewise,” they say, “replacing saturated fat with unsaturated fat was associated with a lower risk of heart disease and mortality.”
For these reasons, the investigators thought it was important to identify and emphasize any associations between different diet types, different quality diets, and mortality risk.
For their study, the researchers analyzed the data of 37,233 U.S. adults with a mean age of 49.7 years. The data came from eight cycles of the National Health and Nutrition Examination Survey (NHANES), from 1999 to 2014.
In total, the follow-up period accounted for 297,768 person years. This refers to the amount of follow-up time for all the participants included in the NHANES surveys.
During this time, the researchers recorded a total of 4,866 deaths, of which 849 were related to heart disease and 1,068 were related to cancer.
Using the NHANES reports regarding people’s macronutrient consumption, the researchers were able to infer different diet quality types.
The team found no association between overall low carb and low fat diet scores and total mortality risk.
However, they did find an association between unhealthful low carb and low fat diet scores — indicating adherence to poor quality low fat and low carb diets — and a higher total mortality risk.
On the other hand, better quality low fat and low carb diets were associated with a lower total mortality risk.
The researchers also report that “participants with a higher overall [low carb dirt score] score” — indicative of a poorer quality diet — “were more likely to be older and non-Hispanic white, to have higher [body mass index], educational level, income level, and cholesterol intake, and to have lower total energy intake.”
As for those with higher low fat diet scores, the investigators point out that they tended to be part of an ethnic minority group, to not smoke, to have lower weights, and to have lower cholesterol levels.
When trying to find an explanation for the association between different diet quality types and mortality risk, Dr. Shan and colleagues point out that many biological mechanisms could play a role.
They write, “Fat provides more than twice as much energy as carbohydrates and protein by weight. A high saturated fat diet is highly palatable and may […] [lead] to overconsumption and obesity.”