Calorie restriction and bone health in young, overweight individuals

Abstract

Background: Calorie restriction (CR) is promoted to increase longevity, yet this regimen could lead to bone loss and fracture and therefore affect quality of life.

Methods: Forty-six individuals were randomized to 4 groups for 6 months: (1) healthy diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 25% energy deficit by a combination of CR and increased aerobic exercise (CR + EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group). Bone mineral density (total body and hip by dual-energy x-ray absorptiometry) and serum bone markers (bone-specific alkaline phosphatase, osteocalcin, cross-linked C-telopeptide of type I collagen, and cross-linked N-telopeptide of type I collagen) were measured at baseline and after 6 months.

Results: Mean +/- SE body weight was reduced by -1.0% +/- 1.1% (control), -10.4% +/- 0.9% (CR), -10.0% +/- 0.8% (CR + EX), and -13.9% +/- 0.7% (LCD). Compared with the control group, none of the groups showed any change in bone mineral density for total body or hip. Bone resorption by serum cross-linked C-telopeptide of type I collagen was increased in all 3 intervention groups, with the largest change observed in the LCD group (CR, 23% +/- 10%; CR + EX, 22% +/- 9%; and LCD, 74% +/- 16% vs control, 4% +/- 10%). Serum levels of cross-linked N-telopeptide of type I collagen were also increased in the LCD group. With regard to bone formation, bone alkaline phosphatase levels were decreased in the CR group (-23% +/- 10%) but were unchanged in the CR + EX, LCD, and control groups.

Conclusions: Moderate CR, with or without exercise, that preserves calcium intake for 6 months leads to large changes in body composition without significant bone loss in young adults. Longer studies with assessments of bone architecture are needed to confirm that CR nutrient-dense diets have no deleterious effect on bone health.

Trial registration: clinicaltrials.gov Identifier: NCT00099151.

Figure 1

Effect of different modes of calorie restriction (CR) on weight as previously shown, (A) and body composition changes (fat mass and fat-free mass) (B) after 24 weeks. The study participants were randomized into 1 of 4 groups for 24 weeks: (1) healthy weight maintenance diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 12.5% CR and 12.5% increase in energy expenditure through structured aerobic exercise (CR+EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group).

Figure 2

Changes in bone mineral density (BMD) (A and B), bone mineral content (BMC) (C and D), and bone area (E and F) across the whole body and the total hip areas after 6 months of calorie restriction (CR). Each box plot shows the distribution of BMD from the 25th to the 75th percentile. The line inside each box plot represents the median. The whiskers reflect the interval between the 10th and the 90th percentiles. The line of identity is also shown. The asterisk indicates significant within-group difference (P<.05). The study participants were randomized into 1 of 4 groups for 24 weeks: (1) healthy weight maintenance diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 12.5% CR and 12.5% increase in energy expenditure through structured aerobic exercise (CR+EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group).

Figure 3

Changes in markers of bone formation (bone alkaline phosphatase [A] and osteocalcin [B]) and bone resorption (serum cross-linked N-telopeptide of type I collagen [sNTx] [C] and serum cross-linked C-telopeptide of type I collagen [sCTx] [D]) after 6 months of calorie restriction (CR). Each box plot shows the distribution of bone mineral density from the 25th to the 75th percentile. The line inside each box plot represents the median. The whiskers reflect the interval between the 10th and the 90th percentiles. The line of identity is also shown. Asterisks indicate significant within-group difference (P<.05). The study participants were randomized into 1 of 4 groups for 24 weeks: (1) healthy weight maintenance diet (control group); (2) 25% CR from baseline energy requirements (CR group); (3) 12.5% CR and 12.5% increase in energy expenditure through structured aerobic exercise (CR+EX group); and (4) low-calorie diet (890 kcal/d; goal, 15% weight loss) followed by weight maintenance (LCD group). BCE indicates bone collagen equivalents.