High body fat percentage with normal BMI increases osteoporosis, sarcopenia risks
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Older adults without obesity, but with a high body fat percentage, have greater risks for sarcopenia and osteoporosis when compared with individuals with obesity, according to findings published in Obesity.
“We observed that most older patients who are normal weight have high amounts of adiposity, which indicates that BMI assessments alone may not be the optimal method for estimating risk for obesity-related health disorders, and particularly for musculoskeletal health outcomes,” David Scott, PhD, associate professor at the Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Australia, told Healio.
Scott and colleagues analyzed data from 3,411 adults aged 70 years in the Healthy Aging Initiative conducted in Umea, Sweden. All participants had clinic measurements as well as areal and volumetric bone mineral density measured at baseline. Baseline data on sarcopenia and osteoporosis were collected, and handgrip strength of the nondominant hand was measured. At follow-up 6 and 12 months after baseline, participants were contacted by phone to detail the number of low-energy falls they experienced in the past 6 months.
Researchers defined individuals with a BMI of 30 kg/m2 or higher as having obesity. Adiposity was defined as having a total body percentage of 25% or higher for men and 35% or higher for women. Participants were split into three groups: normal adiposity and normal BMI, high adiposity and normal BMI, and high adiposity and high BMI. Out of the study cohort, 68.1% of participants were in the high adiposity and normal BMI group, with 17.7% having high adiposity and high BMI, and 14.2% having normal adiposity and normal BMI.
Lower muscle, bone strength with high adiposity
The high adiposity-normal BMI cohort had lower total trabecular bone area at the distal radius than the other two groups as well as lower bone area at the distal tibia compared with the high adiposity-high BMI group. At the proximal radius, high adiposity-normal BMI individuals had a lower cortical area, cortical thickness and strain-stress index compared with the high adiposity-high BMI group, as well as lower periosteal and endosteal circumferences than both groups. The high adiposity-normal BMI group had lower values in all proximal tibia parameters except for cortical BMD and strain-stress index when compared with high adiposity-high BMI individuals. When compared with the normal adiposity-normal BMI group, the high adiposity-normal BMI cohort had lower values for strain-stress index and endosteal circumference in the proximal tibia.
“We were somewhat surprised to observe that older adults with normal BMI and high adiposity had lower muscle strength and poorer bone quality than those with normal BMI and normal adiposity, despite having greater muscle mass and higher BMD,” Scott said. “This adds to the growing evidence that adiposity in and of itself is not beneficial for muscle and bone health in older populations.”
Prevalence of osteoporosis, sarcopenia
Among the study population, 41.4% met the criteria for osteopenia and 13% for osteoporosis, and 1.9% had probable or confirmed sarcopenia. There were 266 adults who reported a single fall of 2,538 who provided complete fall records; 36 individuals said they had more than one fall.
After adjusting for confounding factors, the high adiposity-normal BMI cohort was more likely to have sarcopenia than those with high adiposity and high BMI (OR = 3.99; 95% CI, 1.41-11.32). Adults with high adiposity and normal BMI were also more likely to have osteopenia and osteoporosis than high adiposity-high BMI individuals (OR = 2.91; 95% CI, 2.35-3.61). The high adiposity-high BMI group was more likely to report falls than the normal adiposity-normal BMI cohort (OR = 1.98; 95% CI, 1.2-3.26).
“Our findings demonstrated that over two-thirds of older adults have normal BMI but high adiposity,” Scott said. “Importantly, these older individuals with normal BMI but high adiposity have an increased risk for osteoporosis and sarcopenia, and similar risk for falls, compared with those we traditionally consider to be obese.
“Further prospective studies are required to determine whether the compromised muscle and bone health observed in those with normal BMI but high adiposity leads to increased risk of fracture over the long term,” Scott said. “If proven to be the case, this may support the need for clinical fracture prediction tools to include body composition rather than body mass measurements. However, we also need further research to explore the feasibility of body composition assessment, which is challenging in many clinical settings.”
For more information:
David Scott, PhD, can be reached at d.scott@deakin.edu.au
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