(P03-004-25) Time-Restricted Eating Differentially Affects Bone Health and Visceral Adipose Tissue in Older Women During Caloric Restriction

Objectives: Most Americans are living with overweight or obesity and eat over 12 hours a day. Calorie-restricted diets (CR) induce weight loss to improve health; however, CR reduces nutrient intake and causes reductions in fat-free soft tissue (FFST) and bone. Extended eating windows (≥ 12 hours) disrupt circadian rhythms and negatively affect bone and body composition. Time-restricted eating (TRE) shortens eating windows to improve health, but TRE studies that include CR, especially in older adults, are limited. We examined the effects of TRE+CR on bone, body composition, and nutrient intake compared to CR alone in older women.

Methods: Postmenopausal women (BMI ≥ 25 kg/m2, 50-79 years old) were randomized to 6 months of TRE+CR (n=26) or CR alone (n=23). TRE+CR self-selected a ≤ 9-hour eating window that ended 4 hours before their usual bedtime. The CR alone group followed their typical eating window. Both groups were provided a daily 50+ multivitamin/mineral and asked to attend counseling sessions to reduce calorie intake. Participants recorded 3-day food records at weeks 0, 6, 12, and 24. Bone mineral density (BMD) and body composition were assessed by dual-energy x-ray absorptiometry at 0 and 24 weeks. Statistical testing included mixed-models analysis.

Results: The women (61 ± 5 years, 71% white, 33 ± 2 kg/m2) had a baseline eating window of 12.3 ± 0.9 hours/day. After the intervention, the eating window decreased by 4 hours in the TRE+CR group (8.1 ± 0.8 h) but did not in the CR alone group (12.7 ± 0.9 h) (p < 0.001). As intended, both TRE+CR and CR had a decrease (p < 0.001) in calorie intake (-447 ±149 vs -348 ±229 kcal/d), all macronutrients, and body weight (-7.5 ± 4.6 vs -6.1 ± 5.4 kg) that did not differ significantly between groups. Fat mass and FFST decreased (p < 0.001) similarly in both groups, yet the loss of visceral adipose tissue (VAT) was greater in TRE+CR vs CR group (-0.40 ± 1.0 vs. -0.14 ± 0.5 kg; p=0.01). In TRE+CR, BMD loss was attenuated at the 1/3 radius vs CR (0.009 ± 0.031 vs -0.019 ± 0.032 g/cm²; p< 0.001). Hip BMD decreased (p < 0.05) and lumbar spine tended to decline (p=0.08) without a difference between groups.

Conclusions: TRE attenuated BMD loss at the radius and increased VAT loss without differentially altering body weight or nutrient intake in older women. Mechanisms to explain the bone and fat changes are currently being examined in the lab.

Funding Sources: NJ-IFNH; USDA-NIFA