Can you provide a respectful way to tell a parent their child "is overweight"
In a medical setting, discussing weight can be a very sensitive subject. Can you describe some respectful and tactful ways to say you (or your child) is overweight?
9 Answers
Do you have charts? We have charts at work which show weight against height and are shaded to show whether you, or your child, fall within the underweight, ideal weight or obese categories. They are nice and scientific looking so it is harder to disagree with them, and each category has a range, so there is less scope to argue about big bones and such like.
That way it isn't you telling them their kid is fat it is some faceless, and nameless, scientist.
Well, everyone's given nice, Politically Correct answers, so I reckon I might as well go the full nasty and say what people really think when they're being all nice and polite:
Yo boy is so fat last time he seen 90210 is on the scale
Yo gal is so big when God said let there be light, he asked her to move.
Yo boy is so fat, when he walks out of the candy store with a red turtle neck on people start yellin "Kool Aid".
Yo gal is so fat she uses the ocean as a bath tub
Yo boy's so fat when he walked by a construction site they used him as a wrecking ball.
Yo gal's Soooooooo Fat...... A Car Crashed Into Her And She Said, "Who Threw That Rock?!"
Yo boy's so fat I get lost around him
Yo gal is so fat she got in a monster truck and made it a lowrider!
Yo boy is so fat he tried to take a bath but the water jumped out!
The chances are that Mum and Dad already know that their child is fat and you won't get any points for restating the obvious. I'd frame it in terms of an overall review of things pertaining to a healthy lifestyle focusing on diet, exercise (lots of positives) and finally talk about BMI rather than weight and associated long term health risks.
Estoy un poco preocupado que su hijo/a está poniendo demasiado peso para su edad...
El aumento de peso de su hijo/a me preocupa un poco...
El exceso de peso no es saludable.
As for tactfulness, not too sure how one fares with the others... short of saying, hey, s/he is getting pleasingly plump! 
Tu hijo (o usted) tiene sobrepeso.
Honestly, this is a difficult thing in any language. Try to explain it from a medical stand point, so you don't sound judgmental. No guarantees though.
Hmm... Isn't there a refrán that's says something like, "En la boca cerrada no entra moscas?" That's not really right for this occasion, though.
You could say,
Estoy preocupo porque cada vez que lo veo su hijo se puse mas en gordo.
On second thought, you'd better not say that, that wouldn't be the most tactful way to say it.
I lived with a Mexican family (and 3 other boarders, all Mexican) last winter in the state of Guanajuato. Grandma and Grandpa, one of their daughters (divorced), and her 2 children. The 6 year old boy was addicted to sweets, and clearly headed (in my opinion) for a life of obesity and probable diabetes and ill health. He was a sweet boy and my friend, in a way, and I never articulated my concerns. I think it would not have gone over well at all. I did discuss it with the boy's aunt, who is and was a good friend, and she shared my concern, but felt as well it would have been received defensively and with no good result.
Good on you for your concern. It's a hard thing to intervene. If you have a somewhat more distant or authoratative relationship, it would be easier. Obesity is such a huge problem the world over.
Su hijo está sobre el peso debido 
"Ummm, __________, your child is overweight."
