Calcium, dairy products, and energy balance in overweight adolescents: a controlled trial

Abstract

Background: Dairy product and calcium consumption have been associated with modifying body fat and body weight in children and adults.

Objective: In overweight adolescent boys and girls, we aimed to determine the effect of the doubling of habitual calcium intake to the recommended intake from dairy or calcium carbonate on energy balance and purported mechanisms including fecal fat excretion, macronutrient use, and parathyroid hormone suppression.

Design: Twenty-five girls with a mean (±SD) BMI (in kg/m(2)) of 33 ± 5 and 17 boys with a BMI of 28 ± 5, aged 12-15 y, participated in two 3-wk controlled feeding sessions that used a crossover design in random order as a summer research camp. In one session, 756 mg Ca/d was consumed; in the other session, an additional 650 mg Ca/d was provided as dairy or calcium carbonate supplements that were matched to the control in macronutrient content. Total energy and macronutrient intakes were controlled and were the same for the 2 sessions for each subject. Primary outcome measures were energy balance, fecal fat excretion, lipid oxidation, and postprandial energy expenditure.

Results: There were no effects of quantity or source of calcium on energy or fat balance, despite calcium-induced increases (P <0.01) in postprandial serum parathyroid hormone suppression.

Conclusion: These data lend little evidence to support the proposed mechanisms for the relation between an increase in calcium intake from calcium carbonate or dairy and weight loss or weight maintenance in children. This trial was registered at clinicaltrials.gov as NCT00592137.

FIGURE 1.

Changes in fat excretion compared with changes in fecal calcium (in g/d) with increased calcium intake from either dairy or CaCO₃ supplementation in adolescents (closed diamonds; n = 32).

FIGURE 2.

Mean (±SEM) values of postprandial energy expenditure in overweight male (solid bars; n = 16) and female (open bars; n = 24) adolescents after consumption of either a dairy product (n = 9 males and 12 females) or a CaCO₃ product (n = 7 males and 12 females) and a control product (n = 16 males and 24 females). Different superscript letters represent significant differences at P < 0.05 (ANOVA).

FIGURE 3.

Mean (±SEM) values of postprandial substrate oxidation (open bars denote protein, dotted bars denote fat, and solid bars denote carbohydrate) in overweight male (n = 16) and female (n = 24) adolescents after consumption of either a dairy-based product (n = 9 males and 12 females) or a CaCO₃ product (n = 7 males and 12 females) and a control product (n = 16 males and 24 females). Values were compared by using ANOVA.

FIGURE 4.

Mean (±SEM) values of the effect of dietary calcium source on serum PTH response to a test meal in 38 adolescents. A: Serum PTH was assessed after a meal challenge comprising an intervention product (main effect of treatment, P = 0.0003; time by treatment interaction, P = 0.02). PTH amounts are indicated for the control (closed circles; n = 38), dairy (closed triangles; n = 19), and CaCO₃ (open circles; n = 19). B: Results were quantified and expressed as the AUC from baseline. *Significant difference between zero and the control group. C: Subjects were categorized by basal PTH concentrations [basal PTH concentration <25.7 pg/mL (Low: dairy, n = 14; carbonate, n = 11); basal PTH concentration ≥25.7 pg/mL (High: dairy, n = 5; carbonate, n = 8]. *Significant difference between zero and low-basal-PTH group given the same intervention product. PTH, parathyroid hormone.