Long-term effects of a very-low-carbohydrate weight-loss diet and an isocaloric low-fat diet on bone health in obese adults

Objective: Compromised bone health is a frequently cited concern of very-low-carbohydrate (LC) diets, although limited data are available from long-term, well-controlled, randomized studies. This study compared the effects of an energy-restricted LC diet and traditional, higher-carbohydrate, low-fat (LF) diet on bone health after 12 mo. Methods: One hundred eighteen abdominally obese adults were randomized to consume either an energy-restricted (similar to 6-7 MJ/d [similar to 1450-1650 kcal/d]), planned isocaloric LC, or LF diet for 12 mo. Body weight, total body bone mineral content and bone mineral density (BMD), and serum bone crosslaps were assessed pre- and postintervention. Results: Sixty-five participants completed the study (LC = 32, LF = 33; age: 51.3 +/- 7.1 y; BMI: 33.4 +/- 4.0 kg/m(2)). Weight loss was similar in both groups (LC: -14.5 +/- 9.8 kg, LF: -11.7 +/- 7.3 kg; P = 0.26). By 1 y, total body bone mineral content had not changed in either group (LC: 2.84 +/- 0.47 to 2.88 +/- 0.49 kg, LF: 3.00 +/- 0.52 to 3.00 +/- 0.51 kg; P = 0.07 time x diet effect). In both groups, total body BMD decreased (LC: 1.26 +/- 0.10 to 1.22 +/- 0.09 g/cm(2), LF: 1.26 +/- 0.09 to 1.23 +/- 0.08 g/m(2); P < 0.001 time) and bone serum crosslaps increased (LC: 319.3 +/- 142.6 to 396.5 +/- 172.0 ng/L, LF: 276.3 +/- 100.6 to 365.9 +/- 154.2 ng/L; P < 0.001 time) independent of diet composition (P >= 0.25 time x diet effect). Future studies would be strengthened by the assessment of regional BMD at clinically relevant sites (i.e., hip and spine) and multiple markers of bone turnover. Conclusions: Weight loss following a hypocaloric LC diet compared with an LF diet does not differentially affect markers of bone health over 12 mo in overweight and obese adults. (C) 2016 Elsevier Inc. All rights reserved.