10/20/2026
The most careful low-fat versus low-carb comparison we have is DIETFITS, published in JAMA in 2018.
Gardner and colleagues randomized 609 adults to a healthy low-fat or a healthy low-carbohydrate diet for twelve months, with real dietitian support in both arms.
At twelve months the low-fat group had lost 5.3 kg and the low-carb group 6.0 kg. The difference between them was 0.7 kg, with a confidence interval that included zero.
Twelve months, six hundred people, and the diet you pick was not the variable that mattered.