What about just carbohydrates and still eating fats?

here is the study directly: https://www.sciencedirect.com/science/article/abs/pii/S0022316623721986?via%3Dihub

food frequency questionnaire (how accurate are old people at reporting "What" they actually ate?)

in this cohort review, Low Carb is <40% of daily food intake as carbohydrates.