Prevention of Obesity in Toddlers (PROBIT) Trial.

INTRODUCTION:

Childhood overweight and obesity represent a serious public health emergency for most western and westernized countries. In fact, obesity prevalence has been increasing for several decades in these countries and weight excess is associated with severe psychological and physical complications, such as depression, diabetes, infertility and cardiovascular disease. As a consequence, childhood obesity is associated with a significant increase of the risk of premature death from endogenous causes. In the Northern Italy, the overall prevalence of overweight/obesity among school children is 25 to 33%, among the highest in Europe.

Childhood overweight and obesity are chronic diseases, with low rate of resolution either spontaneous or following medical care, and with high rates of persistence into adulthood as well as worsening and/or relapse after temporary improvements. Thus, prevention is recognized as the most promising strategy to combat the obesity epidemic during childhood.

The meta-analysis of pediatric prevention trials has highlighted a poor effectiveness of interventions targeting school children and a scarcity of data on interventions targeting the infancy. This is internationally recognized as an important gap of the state of the art on obesity prevention. In fact, the mechanisms leading to obesity may be triggered, in most children, during the first months or years of life, making preventive interventions too late and non effective for several children who are already overweight or obese at three years of age. The few existing prevention trials targeting pre-school children have been more encouraging than those concerning school-age, especially when considering interventions based on the education of parents rather than on modifications of extra-family environment (kinder-garden, etc…).

There are several known modifiable risk factors for early growth acceleration, which may inspire potentially effective interventions to prevent overweight and obesity in toddlers. These risk factors concern breast feeding, complementary feeding, nutrition during the first and second year of life, parenting style, feeding practices (i.e. scheduled feeding, responsive feeding, feeding to calm, etc…), and overall lifestyle (active play and sleeping patterns).

The PROBIT trial aims to decrease the prevalence of overweight/obesity at two years of life, in a group of toddlers whose parents are provided with an intensive standardized educational intervention from their child' s birth onwards (intervention arm), compared to a group of toddlers whose parents are not provided with any additional intervention besides the usual care and follow-up provided by their paediatrician (control arm).

The secondary aims of the trial are:

• to improve the feeding practices during the first two years of life in the intervention group compared to the control group;
• to reduce the prevalence of overweight and obesity at one year of age, in the intervention group compared to the control group.

METHODS:

Eleven primary paediatricians randomized to the intervention group and intensively trained about the trial intervention, were asked to consecutively recruit the parents of at least 30 newborns taken in charge within the first six months of the study, and to provide them with standardized oral and written information on protective practices during all the well visits scheduled in the first two years of the child's life. In particular, according to the intervention protocol, parents were provided with oral and written information on behaviors to adopt for their child to be protected from obesity: breast feeding, feeding on demand, responsive feeding, correct time of introduction of complementary feeding, portions shaped on the child's appetite, avoiding "pressing the child to eat more" and rewarding or punishing the child with food, avoiding added sugar and beverages other than milk and water, practicing active game with the child, alternating protein sources correctly and avoiding protein excess. Written menus examples and coloured photos of average portions were given for complementary feeding. Parents were also provided with information about health consequences of childhood obesity.

Another eleven primary paediatricians were randomized to the control group, and asked to consecutively recruit the parents of at least 30 newborns taken in charge within the six months of the study and to provide them with usual care and follow-up.

When all recruited children completed the second year of life, the two groups of toddlers were compared as regards the prevalence of overweight/obesity, defined by WHO cut-offs of the weight/length ratio.

Statistics:

Arm size calculation: although each arm was recruited and followed-up by eleven paediatricians, the minimal number of newborns for each arm was calculated as for a non clustered trial, based on the assumption of a very low intra-class correlation among the newborns recruited by each single paediatrician. Minimal sample size of each arm was calculated in order to have an 80% power to detect, with 95% of statistical certitude, a 33% reduction of overweight/obesity at 24 months of age in the intervention compared to the control arm. This corresponds to about a 18% and a 27% prevalence in the intervention and control arm, respectively, based on epidemiological data from the Northern Italy (Obesity 2006; 14(5):765-9.). The calculation was performed with G power software (http://www.gpower.hhu.de/) and resulted in a minimal number of 330 newborns per arm, which is the reason why each of the eleven paediatricians participating in either arm was asked to recruit at least 30 newborns.

Statistical analyses: rates of overweight/obesity were compared across the two arms by Chi Squared test. Moreover, a binary logistic model was run, with overweight/obesity as dependent variable and arm, parental BMI and parental socio-economic status as independent variables.

The same type of analysis was performed for secondary binary outcomes (rate of overweight/obesity at one year of age, rate of beverage consumption, etc...).

Continuous variables (BMI, weight/lenght ratio) were compared across the two arms by general linear models, with arms as fixed factor and parental BMI and socio-economic status as co-variates.