Non-alcoholic fatty liver disease is becoming increasingly common in Canada and throughout the world. Fatty liver can increase the risks of perioperative complications for those who need liver surgery. A ketogenic diet is low in carbohydrates and can be very effective in reducing liver fat content. The purpose of this randomized control trial is to compare the effect of a short duration (4 week) preoperative ketogenic diet on operative and disease outcomes in patients undergoing liver surgery. One arm will be randomized to the ketogenic diet and the other will receive standard of care pre-operative dietary consultation.

The rise in obesity has contributed to increasing rates of non-alcoholic fatty liver disease (NAFLD) in Canada and globally. In the setting of liver surgery, fatty liver has been associated with higher rates of blood loss during surgery as well as higher rates of postoperative complications. A pre-operative ketogenic diet (KD) has been proposed as a strategy to decrease the risks of fatty liver in patients undergoing liver surgery and has shown promising results in reducing liver fat content, even with short-duration diets. The current literature contains a large variety of pre-operative diets aimed at reducing liver fat content and most studies are observational. Presently, there is no randomized control trial looking at the effects of a well-formulated and standardized KD prior to liver surgery and its effect on operative and disease outcomes. This study will randomize patients with NAFLD needing surgery to remove liver tumors to either the control group or intervention group. Patients in the control group will receive dietary consultation for a standard of care diet as recommended by Canada's Food Guide. Patients in the intervention group will consult with a dietician before starting a 4-week preoperative well-formulated very low carbohydrate KD. All participants will track daily nutritional intake and provide weekly summary reports via an app called Cronometer. The investigators will analyze differences in intraoperative blood loss and OR time, postoperative complications, disease recurrence and mortality rates between the two groups.

Inclusion Criteria:

• Patients 18 years of age or older undergoing any type of liver resection (e.g. wedge, formal hepatectomy), either open or laparoscopic, for colorectal liver metastases (CRLM)
• Patients with evidence of hepatic steatosis on pre-operative imaging (CT or MR) or biopsy.
• Ability to use an app based nutritional program to track macronutrient uptake throughout the dietary intervention.

Exclusion Criteria:

• Patients undergoing liver resection for any other indication
• Patients on sodium glucose co-transporter 2 (SGLT-2) inhibitors (these are contraindicated with a ketogenic diet).
• Patients without evidence of hepatic steatosis.
• Patients with evidence of liver fibrosis or cirrhosis on preoperative bloodwork or imaging.
• Patients with alcohol-related hepatic steatosis.
• Patients with a known bleeding disorder.

The surgeons, surgical team, and data abstractors will be blinded to participant randomization