Ah yes, the most asked question in all weight loss-groups known to man. The equivalent of to crossfit or not to crossfit, and the closest most nutrition people come to being part of a science-denying cult. For some reason, there is no middle way on this one; you´re either for or against, and if you are too smart/chickenshit not to choose, you know nothing.
Luckily, a newly published meta-analysis of 32 controlled feeding studies seems to have settled the case. This effectively means that, in 5-10 years, the majority of people in the fitness/nutrition industry will know and talk proudly about this.
In short, low-fat diets showed to elicit the greatest increases in fat loss.
Below is the abstract and a forest-plot of the included studies and their results.
Weight changes are accompanied by imbalances between calorie intake and expenditure. This fact is often misinterpreted to suggest that obesity is caused by gluttony and sloth and can be treated by simply advising people to eat less and move more. Rather various components of energy balance are dynamically interrelated and weight loss is resisted by counterbalancing physiological processes. While low-carbohydrate diets have been suggested to partially subvert these processes by increasing energy expenditure and promoting fat loss, our meta-analysis of 32 controlled feeding studies with isocaloric substitution of carbohydrate for fat found that both energy expenditure (26 kcal/d; P <.0001) and fat loss (16 g/d; P <.0001) were greater with lower fat diets. We review the components of energy balance and the mechanisms acting to resist weight loss in the context of static, settling point, and set-point models of body weight regulation, with the set-point model being most commensurate with current data.