Does a low-fat diet slow down skin ageing or make it worse?

None of the studies in these sources directly compares a low-fat diet with a high-fat diet on skin ageing in humans. That fundamental question therefore remains unanswered in the available literature. What does exist are separate puzzle pieces, each of which illuminates only part of the picture.

Mouse studies show that a high-fat diet stimulates the mobility of skin cells (fibroblasts) and the amount of subcutaneous fat tissue more strongly than a low-fat diet. Whether that is beneficial or detrimental for skin ageing in humans is not known from these sources.

A narrative review (an overview article without a statistical summary of studies) concludes that a high-fat diet, refined sugars, and certain food additives are bad for the skin. At the same time, that same review points to the benefits of antioxidant-rich food and a diet low in fast-absorbing sugars. However, a narrative review does not provide hard certainty.

The only concrete study conducted in humans concerns almonds: a small RCT suggests that daily almond consumption (roughly a handful per day, rich in healthy fats) may protect the face against ageing caused by UV radiation. This is specific to almonds, however, not to fats in general, and the evidence is preliminary.

All in all, direct comparative research in humans is lacking. Dietary fat is furthermore not a homogeneous category: the type of fat (olive oil versus saturated fat) most likely matters more than the quantity. A strict low-fat diet as a strategy for younger-looking skin currently has no evidential support.