Research

Bone mineral density and content during weight cycling in female rats: effects of dietary amylase-resistant starch

John D Bogden^1,2 , Francis W Kemp¹ , Abigail E Huang¹ , Sue A Shapses² , Hasina Ambia-Sobhan² , Sugeet Jagpal¹ , Ian L Brown³ and Anne M Birkett⁴

¹Trace Element and Mineral Research Laboratory, Department of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School, Newark, NJ, 07103-2714, USA

²Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ 08901, USA

³Faculty of Health and Behavioural Science, University of Wollongong, Wollongong, NSW 2522, Australia

⁴GTC Nutrition, Golden, CO 80401, USA

author email corresponding author email

Nutrition & Metabolism 2008, 5:34doi:10.1186/1743-7075-5-34

Published:	26 November 2008

Abstract

Background

Although there is considerable evidence for a loss of bone mass with weight loss, the few human studies on the relationship between weight cycling and bone mass or density have differing results. Further, very few studies assessed the role of dietary composition on bone mass during weight cycling. The primary objective of this study was to determine if a diet high in amylase-resistant starch (RS₂), which has been shown to increase absorption and balance of dietary minerals, can prevent or reduce loss of bone mass during weight cycling.

Methods

Female Sprague-Dawley (SD) rats (n = 84, age = 20 weeks) were randomly assigned to one of 6 treatment groups with 14 rats per group using a 2 × 3 experimental design with 2 diets and 3 weight cycling protocols. Rats were fed calcium-deficient diets without RS₂ (controls) or diets high in RS₂ (18% by weight) throughout the 21-week study. The weight cycling protocols were weight maintenance/gain with no weight cycling, 1 round of weight cycling, or 2 rounds of weight cycling. After the rats were euthanized bone mineral density (BMD) and bone mineral content (BMC) of femur were measured by dual energy X-ray absorptiometry, and concentrations of calcium, copper, iron, magnesium, manganese, and zinc in femur and lumbar vertebrae were determined by atomic absorption spectrophotometry.

Results

Rats undergoing weight cycling had lower femur BMC (p < 0.05) and marginally lower BMD (p = 0.09) than rats not undergoing weight cycling. In comparison to controls, rats fed RS₂ had higher femur BMD (p < 0.01) and BMC (p < 0.05), as well as higher values for BMD and BMC measured at the distal end (p < 0.001 and p < 0.01) and femoral neck (p < 0.01 and p < 0.05). Consistent with these findings, RS₂-fed rats also had higher femur calcium (p < 0.05) and magnesium (p < 0.0001) concentrations. They also had higher lumbar vertebrae calcium (p < 0.05) and magnesium (p < 0.05) concentrations.

Conclusion

Weight cycling reduces bone mass. A diet high in RS₂ can minimize loss of bone mass during weight cycling and may increase bone mass in the absence of weight cycling.