Cardiff University's Prof Adrian Edwards, who is director of the Health and Care Research Wales Evidence Centre, said the country had a "significant problem" with childhood obesity. He added more than 25% of Welsh children aged four to five were overweight, compared to about 11% across the UK and 7% on average in other high-income countries. "All the health problems we would recognise and understand - including mental health problems, arthritis, high blood pressure, diabetes, cancer risk and all sorts of things - they are higher risk because of overweight and obesity, which starts in childhood," he said. He admitted some scientific research showed BMI was not always accurate. Prof Edwards cited the example of professional rugby players who can score as obese, "but most of them are actually just full of muscle". Another example, he said, was children's bodies changing as they grow. However, he emphasised the need for "a balance to be struck between accuracy and consistency". "They've been doing the same thing over 20, 30 years. "So, leaving aside the nuances of who might or might not be being incorrectly categorised at the edges, I think it's telling us something about the mainstream, the typical picture," he said. "The question is what you do with this information. Is it about diagnosing an individual who should then have some extra attention and support? "Or is it actually about understanding the problem at population level, perhaps without singling out individuals?"