The article is behind a paywall, but I assume they're talking about this https://www.cmaj.ca/content/197/14/E372
From table 1
1.2 Nutrition interventions
We suggest using nutritional interventions for managing obesity in children aged 18 years and younger.
Rationale: For critically important outcomes, no data were available, but for our very important outcome (BMIz), compared with minimal interventions, nutrition interventions had a small beneficial effect. No serious AEs were reported in any nutrition intervention studies. When mild to moderate AEs were reported, they were trivial. This recommendation relates to nutrition interventions exclusively, not in conjunction with other interventions.
This really should be the main focus of their guidance, not a sidenote.... Sugar and carbs are making these kids sick