Fat is not metabolized to glucose and does not require insulin to be metabolized. Instead, a ketogenic diet (high fat diet) provides energy from ketones. Eating only fat will for that reason not increase the blood glucose level.
That may sound good but let us look at what happens. In this study fourteen lean, healthy individuals randomly received either palm oil or a placebo (Hernández EÁ, et al., 2017). The evaluation was very thorough and included among other tests magnetic resonance spectroscopy. This was the result.
Saturated fat ingestion rapidly increased liver fat storage and insulin resistance. The researchers stated that saturated fat may contribute to nonalcoholic fatty liver disease.
What else happens on a ketogenic diet?
When the body burns fat as its main fuel, one of the products produced is acetoacetate. This generates the by-products acetone and acetol. These 2 products are potential precursors of the glycotoxin methylglyoxal.
Methylglyoxal and its byproducts are recognized as a significant cause of blood vessel and tissue damage and was measured together with acetol and acetone in individuals on the Atkins diet (Beisswenger BG, et.al, 2005). The Atkins diet is a ketogenic diet.
The results showed that samples from individuals in ketosis increased the methylglyoxal 2.12-fold, acetol 4.19 and acetone 7.9. There were no changes in samples from noncompliant, nonketotic individuals. This implies that potential tissue and vascular damage can occur.
Beisswenger BG, Delucia EM, Lapoint N, Sanford RJ, Beisswenger PJ.Ketosis leads to increased methylglyoxal production on the Atkins diet. Ann N Y Acad Sci. 2005 Jun;1043:201-10.
Hernández EÁ, Kahl S, Seelig A, Begovatz P, Irmler M, Kupriyanova Y, Nowotny B, Nowotny P, Herder C, Barosa C, Carvalho F, Rozman J, Neschen S, Jones JG, Beckers J, de Angelis MH, Roden M. Acute dietary fat intake initiates alterations in energy metabolism and insulin resistance. J Clin Invest. 2017 Feb 1;127(2):695-708.