A systematic review including 9 studies (7 of which were RCTs) with a total of more than 525 subjects was abstracted in DARE. Studies included overweight or obese children. The studies were combined in a narrative for energy-restricted diets, reduced carbohydrate diets and low glycaemic index diets. None of the included studies reported withdrawals due to side-effects. Energy-restricted diets were associated with a statistically significant greater weight loss at 6 and 12 months compared with a diet with energy intake judged appropriate to physiological requirements (1 study). Relative to no treatment, 1 study showed a lower percentage of overweight children at 6 months (p<0.01), whereas another study reported a non-statistically significant reduction in both weight and body fat in the energy-restricted group.
Low carbohydrate diets were associated with a statistically significant short-term (less than 3 months) reduction in weight and BMI compared with energy-restricted low fat diets (3 studies, p<0.05). One study evaluated the long-term effects and showed a statistically significant reduction in BMI at 10 weeks (p<0.001) and 5.5 months (p<0.05). One study compared two similar energy-restricted medium carbohydrate/high protein diets as part of a 9-month residential intervention and showed comparable weight and BMI reductions in both treatment groups.
Compared with an energy-restricted low fat diet, an ad libitum low glycaemic index diet was associated with a statistically significant weight loss (-2.03 kg versus +1.3 kg, p<0.001) and reduction in BMI (-1.53 versus -0.06, p<0.001) at 17 weeks in 1 study, while another study showed a statistically significant reduction in BMI at 12 months (-1.2 versus -0.6, p<0.02).
Comment: The quality of evidence is downgraded by indirectness (lack of long-term follow-up) and by imprecise results (limited study size for each comparison).