1. A study of the food intake, during a period of 7 consecutive days, was made on 192 boys and girls, aged 14 years, attending Glasgow schools in 1964. A similar study was done in 1971 on 419 boys and girls of the same age. The children came from all the various socio-economic backgrounds and were subdivided into four social groups.
2. The heights and body-weights of the groups studied in 1964 and 1971 were similar but the percentage contribution of fat to the body-weight had increased in the boys.
3. Between 1964 and 1971 there had been a decrease in the mean energy intake of both boys and girls of between 0.8 and 1.0 MJ (200–250 kcal)/d. A similar proportionate decrease had also occurred in the protein, fat, carbohydrate, calcium and iron contents of the diet. However, no individual had a very low intake of protein.
4. Only the boys of the poorest social group (4) showed a lower intake of nutrients than the other groups. There were almost no differences between the girls from the different socio-economic groups.
5. Eating school meals did not affect levels of total energy and nutrient intake.
6. The proportion of energy and nutrients derived from different food groups did not appear to have appreciably altered in the two surveys, although the amount of milk drunk had become less. Fish, eggs and cheese contributed surprisingly little to the diet.
7. The combination, in both sexes, of a reduction in energy intake in 1971 compared to 1964, together with, for the boys, an increased body fat content, could be accounted for by a marked reduction in physical activity.
8. Although a comparison of the energy intake of the fattest and of the thinnest boys showed no clear differentiation, there was a consistently lower energy intake, in all social groups, by the fattest girls (‘fattest’ 7.07 MJ (1690 kcal)/d; ‘thinnest’ 9.23 MJ (2207 kcal)/d).
9. These and other recent results suggest that the national (UK) recommended energy requirements, at least for this group, are too high.