Healthy Weight: Results from Studies in Children and Adolescents

The evidence

In 2023, the Food and Agriculture Organization of the United Nations (FAO) published a global assessment on the role of terrestrial animal-source foods in healthy diets, highlighting milk and dairy products as key contributors to nutrition and health.¹

• In school-age children and adolescents, dairy intake is linked to increased height and lower risks of obesity/overweight.

In 2021, the Milky Way study aimed to determine whether dietary guidelines should continue recommending reduced-fat milk for children.² This double-blind, pilot randomized trial assessed adiposity and biomarkers for cardiometabolic risk in 46 healthy children aged 4-6 over 12 weeks, with participants assigned to either whole-fat or reduced-fat milk while maintaining their usual diets.

No differences were observed between the groups for:

• Adiposity measures, including anthropometrics and body composition;
• Cardiometabolic risk factors, including lipid concentrations, serum glycemic measures, serum inflammatory biomarker fasting C-reactive protein, and systolic and diastolic blood pressure.

In a 2020 systematic review of 29 articles, O’Sullivan et al. evaluated existing literature reporting associations between whole-fat dairy products or reduced-fat dairy products on adiposity and cardiometabolic risk factors in children.³

• Whole-fat dairy intake was not associated with weight gain or increased adiposity.
  • Several studies have found that full-fat dairy was inversely associated with adiposity, a relationship not seen in reduced-fat dairy.
• Whole-fat dairy intake was not associated with higher cardiometabolic or inflammatory biomarkers, though one study found improved outcomes in some risk factors.

A 2020 systematic review and meta-analysis of 14 studies including 20,897 children (ages 1-18 years) evaluated the association between cow’s milk fat consumption and adiposity in healthy children aged 1-18 years old.⁴ The authors note that:

• Whole-fat milk consumption does not negatively affect body weight or composition in children and adolescents; in fact, it is often linked to a lower risk of childhood overweight or obesity.
• Despite some variability across studies, children who consumed whole-fat milk had a 39% decreased risk of being overweight or obese compared to those who consumed reduced-fat milk.

A 2019 meta-analysis of randomized controlled trials published by Kang et al. assessed whether milk and milk-product consumption can affect growth and body composition in children and adolescents.⁵ Their analysis included 17 trials (lasting 3 to 24 months) with a total of 2844 participants, 6 to 18 years of age. The authors concluded that children and adolescents who consume milk and milk products are more likely to achieve a lean body. Compared to controls:

• Interventions with milk and milk products resulted in a greater increase in lean body mass and lower gain in percent body fat. 

A 2017 systematic review of randomized controlled trials by Kouvelioti et al. summarized the effects of dairy food consumption on body size and composition, and bone properties in children and adolescents.⁶ Most studies found that dairy food consumption had favourable effects on bone mineral density and bone mineral content, and a neutral effect with respect to body size (height and weight) or body composition (lean body mass). 

A 2013 meta-analysis of randomized controlled trials and observational studies by Dror evaluated the association between dairy intake and adiposity among preschoolers, school-age children, and adolescents in developed countries.⁷

• Among adolescents, dairy intake was associated with reduced adiposity.
• Among preschool and school-age children, there was no association between dairy intake and adiposity.

A 2015 analysis of data from a randomized controlled trial explored the effects of substituting sugary drinks with alternative beverages (water, milk, and diet drinks) on body weight gain among 366 Danish children aged 2 to 6 years. The trial lasted 1.5 years.⁸

• The substitution of 100 g/d of sugary drinks with 100 g/d of milk was associated with lower BMI and body weight. 

An earlier randomized controlled trial by Albala et al. investigated the effects of replacing sugar-sweetened beverages with flavoured milk.⁹ This study included a total of 98 Chilean children, 8 to 10 years old, who regularly drank sugar-sweetened beverages. The children in the intervention group were provided with and instructed to drink 3 servings of flavoured milk a day for 16 weeks instead. The authors concluded that: 

• Replacing regular consumption of sugar-sweetened beverages with flavoured milk may have beneficial effects on lean body mass and growth in children.

In a 2016 meta-analysis of prospective cohort studies, Lu et al. investigated the long-term association between dairy intake and the risk of childhood obesity.¹⁰ Ten studies comprising 46,011 children and adolescents with an average 3-year follow-up were included. Compared to those in the lowest dairy intake group:

• Those in the highest dairy intake group were 38% less likely to be overweight or obese;
• Each additional serving per day of dairy products was associated with a 0.65% reduction in the percentage of body fat and 13% lower likelihood of overweight or obesity.

The association between milk fat consumption and body mass index was examined in the Early Childhood Longitudinal Survey, Birth Cohort.¹¹ Assessments were performed at 9 months, 2, 4, and 5 years. Data from the 2-year-old and 4-year-old evaluations were used for the study:

• Children who consumed 1% or skim milk were more likely to be overweight and obese compared to those who drank 2% or whole milk;
• Among children who were normal weight at baseline, those who consistently consumed 1% or skim milk were more likely to become overweight or obese.

Using data from the National Health and Nutrition Examination Survey (NHANES 2005–2008), Keast et al. examined the relationship between dairy and yogurt consumption and the risk of obesity in US children aged 8 to 18 years.¹²

• Total dairy consumption was inversely associated with body fat as measured by subscapular skinfold thickness.
• Yogurt consumers had a lower prevalence of overweight or obesity, lower BMI-for-age, lower waist circumference and smaller subscapular skinfold thickness.

Conclusion

Dairy consumption in children and adolescents may have a beneficial effect on body weight and composition.

Replacing sugar-sweetened beverages with milk products, including flavoured milk, is associated with improvements in body composition.

Yogurt, in particular, may be linked with a lower risk of obesity. Additional research is needed to better understand how specific milk products help children and adolescents achieve and maintain a healthy weight.