. . . and what happens at the opposite end of the scales?
So, there are supports for children who are overweight but what happens when a child is deemed underweight?
Jacqueline Rothfork Wogan's experience was mixed. "When our daughter Zoe was born she was quite small and the public health nurses often expressed concern over her weight.
"Despite her being healthy and a happy baby, by the time she was a small child they recommended that we have her checked by a specialist," says Jacqueline.
She was stressed, as she was sure her daughter was fine, but she attended the appointment.
"When we saw the specialist, who was somewhat understanding, he stressed we were to come back again for re-weighing and if there was no improvement.
"I was to stop breastfeeding and put Zoe on to some high-calorie formula along with an appetite stimulant. I left in floods of tears, feeling like a neglectful mother."
Jacqueline continued to be vigilant with Zoe, weighing her daily.
She says: "When I took her to her 18- month check-up, everything was fine except her weight.
"The nurse insisted we feed Zoe Petit Filous 3 times a day and lots of cheese sandwiches on white bread to bulk her up. We are of Vietnamese heritage and dairy is not a major part of our diet, so I was very reluctant to do this."
Even now, at aged four, Zoe is still of slight build but Jacqueline is confident she is feeding what is right for her.
"She is very healthy and has never been on anti-biotics or prescription medicine. Zoe eats little and often, much like her Vietnamese Grandmother. We are all different and diets of a child's native heritage need to be taken into account."
Karl Henry says that with children who are underweight or of slight build, it is important to feed them little and often have a diet packed with protein and wholegrain.
"As for activity, build them up slowly as they will probably have a fast metabolism.
"Do less cardio exercise and make sure they eat every two-three hours. Turkey on wholegrain bread is a great snack when trying to build up weight, and exercise like walking the dog or chasing a rabbit around the garden are good too."