According to the Mirror, the last five years have seen scores of British children taken into care because they’re morbidly obese.

These represent the most extreme cases – but in the population as a whole, over a fifth of Reception Year children (aged 4 or 5) are obese or overweight, as are nearly one third of Year 6 children (aged 10 or 11). Forty years ago, less than a tenth of children were counted as overweight.

It’s no exaggeration to speak of an obesity epidemic, one that has swept across the developed world – and which is taking hold in many developing countries too.

There is, however, some cause for optimism. For instance, America – world famous for its adipose adults and chubby children – appears to have turned a corner in respect to its youngest citizens. Sabrina Tavernise reports on the latest figures for the New York Times:

“Federal health authorities on Tuesday reported a 43 percent drop in the obesity rate among 2- to 5-year-old children over the past decade, the first broad decline in an epidemic that often leads to lifelong struggles with weight and higher risks for cancer, heart disease and stroke…

“About 8 percent of 2- to 5-year-olds were obese in 2012, down from 14 percent in 2004.”

The usual caveats apply – this is just one study and the good news only applies to one age group. On the other hand the study in question is considered to be the “gold standard” of US obesity research, and what happens in early childhood is of life-long significance:

“New evidence has shown that obesity takes hold young: Children who are overweight or obese at 3 to 5 years old are five times as likely to be overweight or obese as adults…

“A third of adults and 17 percent of youths are obese, the federal survey found. Still, the lower obesity rates in the very young bode well for the future, researchers said.”

So, assuming that the figures reflect a genuine improvement, what explains the turn around? There’s little consensus here, but no shortage of theories:

“Children now consume fewer calories from sugary beverages than they did in 1999. More women are breast-feeding, which can lead to a healthier range of weight gain for young children. Federal researchers have also chronicled a drop in overall calories for children in the past decade, down by 7 percent for boys and 4 percent for girls, but health experts said those declines were too small to make much difference.”

Then there’s a possibly significant reform to the US welfare system:

“…the federally funded Special Supplemental Nutrition Program for Women, Infants and Children… which subsidizes food for low-income women, reduced funding for fruit juices, cheese and eggs and increased it for whole fruits and vegetables.”

Of course, unlike in America, the UK welfare system does not subsidise food directly. Proposals to use the tax system to send price signals would impact everyone not just parents of young children.

In any case, there’s evidence of a decline in childhood obesity rates in Britain too – and over much the same time period as the one highlighted by the American study. All that nagging by governments, doctors and the likes of Jamie Oliver might annoy people, but it does appear to be having an effect.

And not before time. Neither Britain nor America can afford to go on paying for needlessly self-inflicted social problems. In an ageing society we’ll have more than enough challenges that we can’t avoid. Do to nothing about the damaging trends that we can reverse is not an option.