Acetyl-CoA can be metabolized through the TCA in any cell, but it can also undergo a different process in liver cells: ketogenesis, which produces ketone bodies.[27] Ketone bodies are also produced in mitochondria, and usually occur in response to low blood glucose levels.[28] When glucose levels are low, oxaloacetate is diverted away from the TCA cycle and is instead used to produce glucose de novo (gluconeogenesis). But when oxaloacetate is unavailable to condense with acetyl-CoA, acetyl-CoA cannot enter the cycle, and so the body has evolved an alternative way to harvest energy from it.
You could certainly use butter, but I’m not sure how that would be more appealing to him if he thinks fat is the enemy. It’s tough to get heart patients to go against the “conventional wisdom” we’ve been fed for so many decades. They have a right to be fearful, but I would suggest offering him research that shows fat isn’t the enemy at all. For what it’s worth, after 6 months of heavy keto (my testing period, though I’ve been keto longer than that) with lots of fats, including butter, bacon, and avocados, my cholesterol and triglycerides dropped! And I’m not the only person to have those same results. Best of luck!

Because people with type 2 diabetes are at an increased risk for cardiovascular disease, there’s a specific concern that the saturated fat in the diet may drive up LDL, or “bad,” cholesterol levels, and further increase the odds of heart problems. If you have type 2 diabetes, talk to your doctor before attempting a ketogenic diet. They may recommend a different weight-loss diet for you, like a reduced-calorie diet. Those with epilepsy should also consult their doctor before using this as part of their treatment plan.