I made a post awhile ago about how whey protein(or proteins with high leucine levels) can spike insulin levels higher than white bread. This study shows similar conclusions when eating high protein meals with either high fat or high carbs, and how it affects body fat storage. This study shows the effects of overeating by 50% of your daily required intake either from carbs or fats in obese vs lean subjects. Insulin levels rose significantly in both groups, however insulin levels increase by 1.6X in the obese group when overfeeding on fats, while decreasing by 50% in the lean subjects(insulin resistance).

Another interesting observation was over feeding with carbs led to an increase in total energy expenditure, while storing 75-85% of the excess calories. In the fat feeding group, no significant increase in energy expenditure and 90-95% of excess calories were stored. In the carb group, a significant decrease in fat oxidation was also noticed(burning less fat). However, when looking at which excess macro was stored, the fat group stored more fat as body fat than the carb group.

This shows that the body is more efficient at storing fatty acids as body fat vs carbs, as I mentioned. Keep in mind, these groups were over feeding by 50% of maintenance. And that obese vs lean store diff macros as body fat differently. Protein intake was constant in both groups. I know this is a lot of info, but I thought it was a really cool study with some interesting conclusions.