Effect of reducing total fat intake on body weight. Hooper et al BMJ 19 January 2013 Vol 346 pg 13

This study looked at 43 trials that assessed the effect of lowering the fat content of people's diet. The lower fat diets were also lower in calories and resulted in small but significant, health wise, drops in weight. This fits with what was previously known and though there were only 4 trials available in children these show the same pattern.