'A Cruel Kindness' begins in a playground, comparing two children on the verge of obesity. The home life of one, Ronnie Brown, is shown: both his mother and father are overweight, family mealtimes are a feast of stodgy treats, and both work and leisure are sedentary activities. Overweight children are at risk of a lifetime of ill-health, and the film lays the blame for childhood obesity clearly on mothers who over-feed their children.

The film addresses the idea of 'glands' or 'puppy fat' causing obesity, as well as genetic determinism ('we are fat people, that's all there is to it,' says Ronnie's mother) before dismissing them and making the case that a healthy weight can be gained from exercise and a balanced diet. The disadvantages of obesity reach beyond health: a third child Valerie, suffers from social exclusion and isolation because of her weight.

'A Cruel Kindness' might seem both simplistic and moralistic by today's standards in largely blaming mothers and family for obesity rather than media-dominated lifestyles or packaged food. But mothers are clearly the film's intended audience, not only for the nutritional information, but also for a moral message about childcare. At the end of the film, the GP addresses mothers directly, telling them that 'it's a cruel kindness to let your children eat too much'.

Director Winifred Holmes had a varied career as a poet, documentarist and journalist. Her interest in nutrition and food was not restricted to this film: during the second world war she worked on the BBC Home Service's 'The Kitchen Front', developing healthy recipes from limited wartime ingredients.