Dr Aaron Carroll explains what a randomised controlled trial is and debunks the hypothesis that Sugar Makes Kids Hyper.
However, he does mention that there is anecdotal evidence that children may have an observable change in behaviour after ingesting sugar[1], however, this does not prove there is a causal link between sugar and hyperactivity in children.
There are many other good reasons why sugary treats should form a very limited part of a child’s diet…but I do find that it is much, much easier to stop random, well-meaning grownups from offering sweets to my kids by saying “No thanks, this stuff makes them start crawling on the ceiling” instead of saying “No thanks, this stuff has little nutritional value and will ruin their appetite. And their teeth.”[2]
By the way, I do like the way that Dr Carroll cuts through the doctorspeak in his video. It’s important to have a doctor that is good at explaining things[3].
1. I draw your attention to the Great Yakult Caper of 2010. The Aged Ps still refer to that event in horrified, hushed tones.
2. The conversation usually goes like this:
Well-meaning auntie/uncle: AIYOH you are SO cute! Come, come, Auntie/Uncle give you sweet!
Debs: Oh, no thank you, they are not allowed any sweets right now.
Horrified auntie/uncle (loudly): WHY CANNOT
Debs: Well…they are going to have lunch soon…
Indignant auntie/uncle: Aiyah, never mind lah, they are just children.
Debs: (feigns desperation) Nooooooo…let me tell you – it’s because they will become (stage whisper) Too Active. (mimes shaky hands)
Understanding auntie/uncle: (nodding sagely) OOooooOOooh. Yah lah, it’s true. (Addresses children) You listen to auntie/uncle – too much sweets is not good for you okay? Now don’t go and give your mummy trouble har.
Debs: YES YES YES LISTEN TO AUNTIE/UNCLE
3. I used to work with a surgeon who would wave his hands mystically over patients, whiffle a little through his moustache and then wander off, leaving me behind to translate in a feeble stammer, “Er…h-h-h-he said that we’ll have to amputate that whole leg. Tomorrow.” Great communicator, that guy.
Owls Well 
I’d also use the trick whereby I take the sweet away and convince the kids that they can have it later or tomorrow… sometimes they forget…
Ha! That doesn’t work for me cos my kids have Very Long Memories.