Rapid Transition from a High-Fat, High-Fructose to a Low-Fat, Low-Fructose Diet Reverses Gains in Bone Mass and Strength.

Purpose: Obesity is thought to negatively impact bone quality and strength despite improving bone mineral density. We hypothesized that 1) continuous consumption of a high-fat, high-sugar (HFS) diet would impair bone quality and strength, and 2) a change from an HFS diet to a low-fat, low-sugar (LFS) would reverse HFS-induced impairments to bone quality and strength.

Methods: Six-week-old male C57Bl/6 mice ( n = 10/group) with access to a running wheel were randomized to an LFS diet or an HFS diet with simulated sugar-sweetened beverages (20% fructose in place of regular drinking water) for 13 wk. HFS mice were subsequently randomized to continuing HFS feeding (HFS/HFS) or transition to the LFS diet (HFS/LFS) for four additional weeks.

Results: HFS/HFS mice exhibited superior femoral cancellous microarchitecture (i.e., greater BV/TV, Tb.N, Tb.Th, and decreased Tb.Sp) and cortical bone geometry (i.e., lower Ct.CSA and pMOI) compared with all other groups. At the femoral mid-diaphysis, structural, but not material, mechanical properties were greatest in HFS/HFS mice. However, HFS/HFS exhibited greater femoral neck strength only when compared with mice assigned to diet transition (HFS/LFS). Osteoclast surface and the percentage of osteocytes staining positive for interferon-gamma were greater in HFS/LFS mice, consistent with reduced cancellous microarchitecture postdiet transition.

Conclusions: HFS feeding enhanced bone anabolism and structural, but not material, mechanical properties in exercising mice. A change from an HFS to LFS diet returned the bone structure to that of continuously LFS-fed mice while compromising strength. Our results indicate rapid weight loss from obese states should be performed with caution to prevent bone fragility. A deeper analysis into the altered bone phenotype in diet-induced obesity from a metabolic standpoint is needed.