Research by the University of Reading has found that couples with children have a poorer diet than those without. On average, statistics showed that childless couples ate 2kg more fruit and vegetables than families over a fortnight. The results formed part of a study that looked at the uneven distribution of unhealthy diets in the population. It also showed that regional variation in the demand for fruit and vegetables is pronounced, with the highest demand in London and the South East and the lowest in Scotland and Northern Ireland.
Professor Richard Tiffin, Director of the Centre for Food Security at the University, said: “There are clear distributional implications for dietary health that arise from these patterns of consumption and also for the health of children. They suggest that targeted interventions are necessary in order to reduce the incidence of diet-related health problems in the future.” The study revealed that the presence of children in a household leads to a lower level of demand for fruit and vegetables and meat, and an increased demand for milk and dairy, cereals and potatoes.
The results also emphasised the role played by low incomes and socio-economic circumstances in poor dietary choices. Comparing an unemployed individual with an otherwise identical individual living in a household of two, the former consumed over 3kg less fruit over a period of two weeks. Similarly, for two identical households, a difference in income of 10 per cent can be expected to lead to a difference in demand for fruit and vegetables of around 500g.
Professor Tiffin said: “Our results imply that households which have a higher level of expenditure will tend to consume proportionately more meat and more fresh fruit and vegetables. Households in London and the South East have higher levels of fruit and vegetable consumption while it is reduced by the presence of children. “The dietary components that we have analysed have important implications for policy-makers in tackling diet-related chronic disease, which represents one of the most significant public health challenges of the 21st century.”
The paper, 'The demand for a healthy diet: estimating the almost ideal demand system with infrequency of purchase, by R. Tiffin (University of Reading) and M. Arnoult (Scottish Agricultural College), is published this month in The European Review of Agricultural Economics – http://erae.oxfordjournals.org/content/current
Researchers used the UK government's Expenditure and Food Survey (EFS) for 2003-2004. Participating households voluntarily record food purchases for consumption at home for a two-week period using a food diary. The sample is based on 7,014 households in 672 postcode sectors stratified by Government Office Region, socioeconomic group and car ownership. It is carried out throughout the UK and throughout the year in order to capture seasonal variations.
Throughout the project, the families received expert guidance from dietitians and were asked to provide blood and urine samples.
Diogenes: The five diet types
The design comprised the following five diet types:
- A low-protein diet (13% of energy consumed) with a high glycemic index (GI)*
- A low-protein, low-GI diet
- A high-protein (25% of energy consumed), low-GI diet
- A high-protein, high-GI diet
- A control group which followed the current dietary recommendations without special instructions regarding glycemic index levels
A high-protein, low-GI diet works best
A total of 938 overweight adults with a mean body mass index (BMI) of 34 kg/sq m were initially placed on an 800-kcal-per-day diet for eight weeks before the actual diet intervention was initiated. A total of 773 adult participants completed this initial weight-loss phase and were then randomly assigned to one of five different diet types, where 548 participants completed the six-month diet intervention (completion rate of 71%).
Fewer participants in the high-protein, low-GI groups dropped out of the project than in the low-protein, high-GI group (26.4% and 25.6%, respectively, vs. 37.4%; P = 0.02 and P = 0.01 for the two comparisons, respectively). The initial weight loss on the 800-kcal diet was an average of 11.0 kg.
The average weight regain among all participants was 0.5 kg, but among the participants who completed the study, those in the low-protein/high-GI group showed the poorest results with a significant weight gain of 1.67 kg. The weight regain was 0.93 kg less for participants on a high-protein diet than for those on a low-protein diet and 0.95 kg less in the groups on a low-GI diet compared to those on a high-GI diet.
The children's study
The results of the children's study have been published in a separate article in Pediatrics. In the families, there were 827 children who only participated in the diet intervention. Thus, they were never required to go on a diet or count calories – they simply followed the same diet as their parents. Approx. 45% of the children in these families were overweight. The results of the children's study were remarkable: In the group of children who maintained a high-protein, low-GI diet the prevalence of overweight dropped spontaneously from approx. 46% to 39% – a decrease of approx. 15%.
Proteins and low-GI foods ad libitum – the way ahead
The Diogenes study shows that the current dietary recommendations are not optimal for preventing weight gain among overweight people. A diet consisting of a slightly higher protein content and low-GI foods ad libitum appears to be easier to observe and has been documented to ensure that overweight people who have lost weight maintain their weight loss. Furthermore, the diet results in a spontaneous drop in the prevalence of overweight among their children.
Citation: Thomas Meinert Larsen, Ph.D., Stine-Mathilde Dalskov, M.Sc., Marleen van Baak, Ph.D., Susan A. Jebb, Ph.D., Angeliki Papadaki, Ph.D., Andreas F.H. Pfeiffer, M.D., J. Alfredo Martinez, Ph.D., Teodora Handjieva-Darlenska, M.D., Ph.D., Marie Kunešová, M.D., Ph.D., Mats Pihlsgård, Ph.D., Steen Stender, M.D., Ph.D., Claus Holst, Ph.D., Wim H.M. Saris, M.D., Ph.D., and Arne Astrup, M.D., Dr.Med.Sc. for the Diet, Obesity, and Genes (Diogenes) Project, 'Diets with High or Low Protein Content and Glycemic Index for Weight-Loss Maintenance', N Engl J Med 2010; 363:2102-2113 November 25, 2010
The authors used survey data from Project EAT (Eating Among Teens), in which two groups of adolescents (1608 middle school and 3074 high school students) completed surveys in 1999 and 2004 regarding eating habits, parental styles, and various socioeconomic variables.
Cross-sectional results for adolescent girls indicated a positive association between maternal and paternal authoritative parenting style and frequency of family meals. For adolescent boys, maternal authoritative parenting style was associated with more frequent family meals. Longitudinal results indicated that authoritative parenting style predicted higher frequency of family meals five years later, but only between mothers and sons or between fathers and daughters.