A recent survey conducted by the South African Medical Research Council shows the prevalence of overweight and obesity among young people aged 13–19 years to be 17% overall, affecting more girls (25%) than boys (7%). Obesity during childhood may manifest into adolescence and adulthood, depending on the length of time being over weight during childhood.

Consequences of obesity in childhood may lead to psychosocial difficulties including discrimination, negative self image and decreased socialisation. It can furthermore lead to increased frequency of hyper lipidaemia, hyper - tension and abnormal glucose tolerance.

The facts

Scientific literature supports the notion that dairy products have a role to play in managing a healthy body weight:

•  An isocaloric, dairy-rich diet, in addition to lifestyle changes, has been shown to be a well-accepted regimen, as well as a safe and practical strategy for weight control in young, overweight children.
• Increased consumption of dietary calcium from dairy sources enhances weight loss, promotes healthy body weight, lowers the percentage body fat and prevents unhealthy weight gain.
• Individuals who consume more calcium from dairy products weigh less and/or have less body fat than those who consume little or no dairy.

Research shows that the consumption of dairy often decreases during adolescent and teenage years because of the perception that dairy is ‘fattening’. Nutritionists have identified the two most important nutrients lacking in the diets of children and adolescents (10–19 years) as calcium and iron. However, calcium-rich foods like milk and dairy products are often the first foods to be discarded by teenagers in their drive to lose weight.

Public health efforts to help adolescents gain access to and choose healthful beverages rather than consuming beverages of minimal nutritional value will contribute to improved dietary intake of dairy products.

The calcium mechanics for weight loss

Research suggests that an inverse relationship exists between calcium intake and body weight, and that calcium may play a role in regulating energy metabolism.

The anti-obesity bioactivity of dairy products is largely attributed to dietary calcium. The bioactivity is primarily localized in the angiotensin-converting enzyme (ACE) inhibitor activity of whey proteins and the high concentration of leucine in whey. This appears to be primarily responsible for the redistribution of dietary energy from adipose tissue to skeletal muscle during weight loss. Therefore, during negative energy balance, more skeletal muscle is preserved and the loss of adipose tissue is accelerated.

Evidence further suggests that high calcium intake results in lower blood parathyroid hormone (calcium regulating hormone) and 1,25 dihydroxyvitamin D concentrations, thereby decreasing intracellular calcium and promoting bone formation and lipolysis. In contrast, low calcium intake causes a rise in parathyroid hormone and 1,25 dihydroxyvitamin D, which results in an increase in intracellular calcium concentrations that promote lipogenesis. Intracellular calcium plays an important role in regulating both lipogenesis and lipolysis in human adipocytes.

Supporting evidence

The role of dairy in weight management of children and adolescents

• The association between dietary calcium and children’s body fat (n = 52, aged 2 months to 8 years, average body mass index (BMI) 17.3 ± 2.1 for boys and 17.1 ± 2.5 for girls), was investigated through the longitudinal monitoring of height, weight, dietary intakes, other related variables and dual energy x-ray absorptiometry (on 8 year old subjects). The study confirmed the negative association between calcium intake and body fat, indicating a 0.4% reduction in children’s body fat when calcium intake was increased through the intake of one glass (8 oz or 237 ml) of milk or yoghurt daily. Despite the relatively small reduction in children’s body fat, a minor decrease in young children’s body fat may reduce the risk of obesity in later life stages.
• A randomised controlled trial of children aged between 8 and 10 years (n=98), who regularly consumed sugar-sweetened beverages, examined the effects of milk beverages compared to sugar-sweetened beverages on body composition. The study recommended that substituting habitually consumed sugar-sweetened beverages with milk could lead to beneficial effects, since the mean increase of lean body mass was significantly better in the group consuming milk (0.92 ± 0.10 kg) than in the control group consuming sugar-sweetened beverages (0.62 ± 0.11 kg).
• Research suggests that adolescent girls may avoid dairy products owing to perceptions that these foods are ‘fattening’. However, a longitudinal study based on the Massachusetts Institute of Technology Growth and Development study of 196 non-obese premenarcheal girls (8-12 years old), indicating that the consumption of dairy products by adolescent girls is not associated with a higher BMI or an increase in the percentage body fat. The dairy products included in this study were low-fat and full-cream dairy products.

The bottom line

As dairy products contain calcium, protein and other essential nutrients, consuming three servings daily, in particular milk, improves the nutritional quality of the diet, whether focused on weight reduction or weight maintenance. Ongoing research aimed at a better understanding of the relationship between dairy and weight management is ongoing. Yet experts already suggest that the emerging role of dairy products is a good reason for people to meet the current dietary recommendations of three servings of dairy per day.

References

Larson NI, et al. 2007. J AmDiet Assoc, 107(9):1502-10
IFIC. 2009
Phillips SM, et al. 2003. Int J Obesity. 27(9):1106-1113
Striegel-Moore RH, et al. 2006. J Pediatr. 148(2):183-187
Theobald HE. 2005. Nutr Bull. 30:237-277
Mahan and Escott-Stump S. 2000. Food, Nutrition & Diet Therapy. 10th edition. Saunders: Philadephia
Kelishadi R et al. 2009. J Am Coll Nutr, 28(5(601-10)
Zemel MB, et al. 2005. Int J Obes. 29(4):341-347
Zemel MB. 2004. Am J Clin Nutr. 79(Supplement):907S-912S
Zemel MB. 2003. Lipids. 38(2):139-146
Zemel MB. 1998. Mol Cell Biochem. 188:129-136
Gunther CW et al. 2005. Am J Clin Nutr. 82:1228-1234
Zemel MB. 2009. Phys Sportsmed. 37(2):29-39
Skinner JD, et al. 2003. J Am Diet Ass. 103(12):1626-1631
Deckelbaum RJ & Williams CL. 2001. Obes Res. 9(Suppl 4):239S-243S
Albala C, et al. .2008. Am J Clin Nutr. 88:605-611.
Moore LL, et al. 2008. J Am Coll Nutr. 27(6):702-710