insulin and ketosis

Studies have shown significant effects on insulin levels and ketosis following MCT ingestion. Insulin levels are of particular interest to low-carb or paleolithic dieters.

Insulin response

In this study, blood ketones were elevated after MCT ingestion, but despite a higher level of ketones which tends to exist with low levels of insulin, insulin was elevated as well. Additionally HGH increased for around 2 hours.

YYY and Zee acknowledge that

Medium-chain triglycerides (MCT) induce ketosis in several mammalian species including man.

Rats were fed either MCT or LCT. Ketone bodies increased 18x only 1 hr after MCT feeding vs 2x for corn oil (LCT). There's more in this lengthy yet concise list of results in the abstract and I suggest you have look. I find the authors' conclusion particularly informative

that ketosis induced by MCT stems from rapid oxidation of medium-chain fatty acids. Hyperinsulinemia, hypoglycemia and depressed lipogenesis resulting from MCT feeding appear to potentiate but not initiate ketosis.

Another study that examined parenteral nutrition for surgery patients demonstrated higher serum levels of insulin in the MCT group than the LCT group.

Chain length matters. The insulin output of capric (C10) and lauric acid is potent and to the magnitude of linoleate.

The insulin level was higher in patients undergoing digestive tract surgery.

MCFAs stimulated insulin secretion in young rabbits, where sunflower oil was ineffective.

Stimulation of insulin by free fatty acids per se was shown to be possible in a study on dogs.

Serum insulin levels in patients with cirrhosis were increased by pure MCTs between 30-120 min after MCT oil ingestion, but not in the fasted state.

No insulin response

Rat study, which compares the insulin response with MCTs vs LCTs

• diets were isocaloric
• dietary forms of MCFA or LCFA are not described

Where LCFAs affected the insulin response, MCFAs showed no effect.

17 healthy young men replaced 70g of their dietary fat with either MCTs or sunflower oil (LCTs). This was achieved by dietary intervention. The subjects were given 1500 calories of 45% fat, 47% carbohydrates,  7% protein. The rest of the subjects' daily intake is not known, except that they were instructed not to consume additional fat.

Fasting insulin was measured and was reported to not significantly differ between the two groups. Even still the fulltext mentions insulin stimulation from high MCT intake in its discussion. The focus of the study was actually on measuring lipid profile.

In 10 NIDDM (diabetes) subjects with 40% fat isocaloric diets, fasting serum insulin was measured to exhibit changes
...
Thus the insulinotropic effects of medium-chain triglycerides appear to be found postprandially.