There was a study done to determine the safety and effectiveness of a Low Carb (LC) diet vs a Calories Restricted Low Fat (CR-LF) diet (J Clin Endocrinol Metab. 2003 Apr;88(4):1617-23. A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. Brehm BJ1, Seeley RJ, Daniels SR, D’Alessio DA.).
The study was on fifty-three healthy, obese female volunteers.
The LC diet was more than twice as effective compared to the LF diet.
The very low carbohydrate diet group lost more weight (8.5 +/- 1.0 vs. 3.9 +/- 1.0 kg; P < 0.001) and more body fat (4.8 +/- 0.67 vs. 2.0 +/- 0.75 kg; P < 0.01) than the low fat diet group.
OK, so the Low Carb diet lost more weight and fat but was it safe? The study looked at the cardio risk factors and concluded.
Mean levels of blood pressure, lipids, fasting glucose, and insulin were within normal ranges in both groups at baseline.
A very low carbohydrate diet is more effective than a low fat diet for short-term weight loss and, over 6 months, is not associated with deleterious effects on important cardiovascular risk factors in healthy women.
So no, not only is Low Carb more effective than Low Fat, but it is also not any less healthy.