The combination of high carb + high fat is very bad. It is also a euphemism for a high calorie diet. In other words, it's the portion sizes that are the problem. It always has been about calories.

However, I'm not so sure that high carb and fat is worse than very high carb. What I mean is, if you are running a calorie excess, I don't think it is better for those extra calories to be carbs as opposed to fat. I think higher fat and lower carb is always the better option, irregardless of total calorie levels. On equal calorie levels, I would expect the lower carb diets to protect metabolic integrity more so than the higher carb diets simply because carbohydrate level is a risk factor independent of total calories for contributing to insulin resistance.

While total energy intake is important, type of energy is also important. Carbs are such a quick burning fuel that in the body they mimic the effects of a high calorie diet, in that they force a great deal of energy in a short period of time. The over abundance of energy necessitates an insulin spike, and if you are insulin resistant the spike might have to be large. This is why insulin resistant people can't lose weight on normal restrictive levels of energy, if that energy is from carbohydrate... simple carbohydrate causes a hormonal reaction that is incongruent with energy intake for them.