One of the most common misconceptions about the ketogenic diet is that it has a negative impact on liver health.
Since the ketogenic diet centers around consuming large amounts of dietary fat, it has been associated with non-alcoholic fatty liver disease (NAFLD). The idea that the ketogenic diet can cause NAFLD is completely unsubstantiated and, in fact, research has shown the exact opposite: that keto can benefit liver health.
A new study published in January 2020 in the journal Applied Physiology, Nutrition, and Metabolism looked at the effects of a ketogenic diet versus a standard western diet on liver metabolism, mitochondrial health, body weight, fat mass, and energy balance.
- Rats fed a ketogenic diet showed improvements in hepatic oxidative stress, reduced lipogenesis, and improvements in mitochondrial health.
- Female rats, specifically, showed improvements in autophagy/mitophagy, and energy homeostasis.
The paper, Ketogenic diet in combination with voluntary exercise impacts markers of hepatic metabolism and oxidative stress in male and female Winsar rats, looked at the effects of exercise plus a ketogenic diet, versus a western diet, and standard chow diet on various hepatic (liver) markers. 
1. Improvements in Hepatic Lipid Metabolism
Lipogenesis is the process by which the body converts acetyl-coA into triglycerides to be stored as fat. Increased levels of lipogenesis mean that the body is storing more fat.
This study showed that the ketogenic diet suppressed lipogenesis (reduction in fatty acid synthase and acetyl-coA carboxylase).
2. Increased Mitochondrial Biogenesis & Mitophagy
Reductions in mitochondrial health have been linked to numerous diseases, including cancer and neurodegenerative diseases. Conversely, mitochondrial biogenesis (the increase in mitochondrial mass) and mitophagy (recycling of mitochondria) have been linked to improvements in disease states and the prevention of numerous health conditions (including aging).
This study showed rats fed a ketogenic diet had increased markers of both mitochondrial biogenesis (specifically PPAR-1a, TFAM, and citrate synthase), as well as mitophagy (specifically LC3 II/I ratio, and ATG 12:5).
3. Reduction in Hepatic Oxidative Stress
Oxidative stress is a process caused by free radicals (oxygen-containing an unpaired electron) that damages cells. Glutathione is an antioxidant that can reduce oxidative stress and prevent this damage to cells. It goes this by giving up an electron so that oxygen can be fully paired and less reactive. In doing so, glutathione is said to be oxidized because it has lost an electron.
This study looked at this process within the liver and found that the ketogenic dieting group had increased levels of hepatic glutathione peroxidase 1 (an antioxidant that reduces peroxides) and a reduction in oxidized glutathione.
This study demonstrates that not only is a ketogenic diet not harmful to liver health, but it may also actually provide numerous benefits. That being said, this research was conducted in animal models, not in humans, and therefore warrants more investigation. The writers of this paper suggest:
“These data highlight that KD and exercise beneficially impacts hepatic metabolism and oxidative stress and merits further investigation.”