Could the timing of sugar exposure matter as much as the amount consumed? Researchers examined diets from pregnancy through toddlerhood to investigate how early nutrition relates to children's developing body composition.
*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
Study: Sex-Specific Associations of Added Sugars and Fructose Exposure Across the First 1,000 Days With Body Composition at 24 Months. Image Credit: Vava Vladimir Jovanovic / Shutterstock
In a recent longitudinal study published on the medRxiv preprint* server, researchers evaluated whether a child's sex modified associations between early dietary sugar exposure and body composition. The investigators analyzed dietary and body-composition data from 130 mother-child dyads across the first 1,000 days (from conception to approximately 24 months) to examine how added sugars and fructose intake during pregnancy and early childhood related to body fat at two years.
The results suggested that associations between dietary sugars and body composition differed depending on developmental timing and the child's biological sex. Prenatal added sugar intake showed stronger positive associations with total and regional fat mass in girls, whereas added sugars during infancy had stronger links with adiposity in boys.
Background
Pediatric research indicates that nutrition during the first 1,000 days represents a critical period of developmental plasticity, when early environmental exposures may influence later metabolic health.
More recent dietary research indicates that excessive consumption of added sugars (AS; sugars added during food preparation or processing) may displace nutrient-dense foods and contribute to excess energy intake, raising concerns about early-childhood diets.
Previous research has linked fructose, in particular, to hepatic de novo lipogenesis (the synthesis of fatty acids in the liver), insulin resistance, and obesity-related metabolic dysfunction. Fructose is present in natural foods, including fruit, and the study did not isolate the effects of particular dietary sources.
Earlier studies frequently relied on weight-for-length (WFL) z-scores or body mass index (BMI) percentiles, which cannot differentiate fat mass (FM) from fat-free mass (FFM; all body components other than fat, including muscle, organs, bone, and water) or quantify regional distribution.
Researchers also recognize that biological sex differences in adipose development emerge early in life, yet few studies have tested whether child sex modifies associations between dietary sugars and body composition across pregnancy, infancy, and toddlerhood.
About the study
The present study examined how dietary sugar intake during pregnancy and early childhood related to body composition at age two, and whether the relationships differed between boys and girls.
The study evaluated mother-child pairs enrolled in two National Institutes of Health (NIH)-funded protocols: the Assessment of Docosahexaenoic Acid (DHA) on Reducing Early Preterm Birth (ADORE) trial, and its offspring follow-up, the Growth and Adiposity in Newborns Study (GAINS), with 130 dyads contributing complete dietary and anthropometric data. This was a secondary observational analysis; sugar intake was not assigned experimentally.
Scientists from the Departments of Dietetics and Nutrition and Biostatistics and Data Science at the University of Kansas Medical Center conducted the research, in collaboration with researchers from the University of Kansas, USA.
Offspring in the study were evaluated at an average age of 24.6 months and included 65 boys and 65 girls, with 66.9% recorded as White and 61.5% as non-Hispanic. Maternal diet was assessed between 12 and 20 weeks of pregnancy. Offspring diet was measured at two weeks, six months, 12 months, and 24 months using a single 24-hour dietary recall at each assessment. Postnatal intakes were averaged to represent Year 1 (infancy) and Year 2 (toddlerhood), and at ~24 months, staff assessed child waist circumference (WC) and skinfold thickness (SKF). Sugar intake was expressed as a percentage of total energy.
Dual-energy X-ray absorptiometry (DXA) scans were attempted across GAINS participants, but only 42 children had complete dietary data and usable scans. These measured percentage body fat (%fat), total FM, FFM, and central and peripheral fat mass.
The study's statistical analyses used multivariable linear regression models to evaluate whether associations differed between boys and girls. These models considered maternal pregnancy characteristics, treatment assignment in the original DHA trial, and child characteristics; final adjustments differed by outcome. Given the limited DXA sample, the authors considered those analyses exploratory and did not adjust for multiple comparisons.
Preprint findings
The results showed different patterns for boys and girls depending on when sugar exposure occurred. In the DXA subset, maternal prenatal added sugar intake was more strongly and positively associated with percentage body fat, total FM, central FM, and peripheral FM in girls than in boys.
In the full cohort, prenatal fructose was more strongly associated with waist circumference in boys than in girls. Prenatal fructose also showed non-significant trends toward stronger associations with selected fat-mass measures in girls.
During infancy, higher added sugar intake was more strongly linked to body fat in boys than in girls, including overall body fat percentage and fat mass in central and peripheral regions. Fructose intake during infancy showed a stronger positive association with fat-free mass in girls than boys.
Finally, the study found that in toddlerhood, fructose was associated with a trend toward a stronger positive association with central skinfold thickness in boys than girls, but this finding was not statistically significant. Sugar intake did not differ significantly by offspring sex in any exposure period.
Conclusions
The present study suggests that associations between early dietary sugar intake and body composition at 24 months may vary with developmental timing and child sex. The findings do not establish that sugars cause changes in body fat, and suggested explanations involving placental biology and infant growth remain untested.
While these results do not yet warrant sex-specific dietary guidelines and require independent replication, they are consistent with recommendations to avoid added sugars before age two. The work has been released as a preprint and has not undergone peer review.
Moving forward, large prospective cohorts that track dietary sources and metabolic biomarkers are required to clarify the mechanisms of pediatric adiposity. Repeated dietary measurements and longer follow-up are also needed to determine whether the associations persist beyond toddlerhood.
*Important notice: medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.
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