Body mass index continues to accurately predict percent body fat as women age despite changes in muscle mass and height

Abstract Background Less than 2% of overweight children and adolescents in Switzerland can participate in multi-component behaviour changing interventions (BCI), due to costs and lack of time. Stress often hinders positive health outcomes in youth with obesity. Digital health interventions, with fewer on-site visits, promise health care access in remote regions; however, evidence for their effectiveness is scarce. Methods This randomized controlled not blinded trial (1:1) was conducted in a childhood obesity center in Switzerland. Forty-one youth aged 10–18 years with body mass index (BMI) > P.90 with risk factors or co-morbidities or BMI > P.97 were recruited. During 5.5 months, the PathMate2 group (PM) received daily conversational agent counselling via mobile app, combined with standardized counselling (4 on-site visits). Controls (CON) participated in a BCI (7 on-site visits). We compared the outcomes of both groups after 5.5 (T1) and 12 (T2) months. Primary outcome was reduction in BMI-SDS (BMI standard deviation score: BMI adjusted for age and sex). Secondary outcomes were changes in body fat and muscle mass (bioelectrical impedance analysis), waist-to-height ratio, physical capacities (modified Dordel-Koch-Test), blood pressure and pulse. Additionally, we hypothesized that less stressed children would lose more weight. Thus, children performed biofeedback relaxation exercises while stress parameters (plasma cortisol, stress questionnaires) were evaluated. Results At intervention start median BMI-SDS of all patients (18 PM, 13 CON) was 2.61 (obesity > + 2SD). BMI-SDS decreased significantly in CON at T1, but not at T2, and did not decrease in PM during the study. Muscle mass, strength and agility improved significantly in both groups at T2; only PM reduced significantly their body fat at T1 and T2. Average daily PM app usage rate was 71.5%. Cortisol serum levels decreased significantly after biofeedback but with no association between stress parameters and BMI-SDS. No side effects were observed. Conclusions Equally to BCI, PathMate2 intervention resulted in significant and lasting improvements of physical capacities and body composition, but not in sustained BMI-SDS decrease. This youth-appealing mobile health intervention provides an interesting approach for youth with obesity who have limited access to health care. Biofeedback reduces acute stress and could be an innovative adjunct to usual care.

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Limitations of body mass index for counseling individuals with unilateral lower extremity amputation

Prosthetics and Orthotics International ◽

10.1177/0309364616650079 ◽

2016 ◽

Vol 41 (2) ◽

pp. 186-193 ◽

Cited By ~ 3

Author(s):

Alexandra P Frost ◽

Tracy Norman Giest ◽

Allison A Ruta ◽

Teresa K Snow ◽

Mindy Millard-Stafford

Keyword(s):

Body Mass Index ◽

Lower Extremity ◽

Health Risk ◽

Body Mass ◽

Body Fat ◽

Lower Limb ◽

Dual Energy ◽

Limb Loss ◽

Percent Body Fat ◽

X Ray

Background: Body composition is important for health screening, but appropriate methods for unilateral lower extremity amputees have not been validated. Objectives: To compare body mass index adjusted using Amputee Coalition equations (body mass index–Amputee Coalition) to dual-energy X-ray absorptiometry in unilateral lower limb amputees. Study design: Cross-sectional, experimental. Methods: Thirty-eight men and women with lower limb amputations (transfemoral, transtibial, hip disarticulation, Symes) participated. Body mass index (mass/height2) was compared to body mass index corrected for limb loss (body mass index–Amputee Coalition). Accuracy of classification and extrapolation of percent body fat with body mass index was compared to dual-energy X-ray absorptiometry. Results: Body mass index–Amputee Coalition increased body mass index (by ~ 1.1 kg/m2) but underestimated and mis-classified 60% of obese and overestimated 100% of lean individuals according to dual-energy X-ray absorptiometry. Estimated mean percent body fat (95% confidence interval) from body mass index–Amputee Coalition (28.3% (24.9%, 31.7%)) was similar to dual-energy X-ray absorptiometry percent body fat (29.5% (25.2%, 33.7%)) but both were significantly higher ( p < 0.05) than percent body fat estimated from uncorrected body mass index (23.6% (20.4%, 26.8%)). However, total errors for body mass index and body mass index–Amputee Coalition converted to percent body fat were unacceptably large (standard error of the estimate = 6.8%, 6.2% body fat) and the discrepancy between both methods and dual-energy X-ray absorptiometry was inversely related ( r = −0.59 and r = −0.66, p < 0.05) to the individual’s level of body fatness. Conclusions: Body mass index (despite correction) underestimates health risk for obese patients and overestimates lean, muscular individuals with lower limb amputation. Clinical relevance Clinical recommendations for an ideal body mass based on body mass index–Amputee Coalition should not be relied upon in lower extremity amputees. This is of particular concern for obese lower extremity amputees whose health risk might be significantly underestimated based on body mass index despite a “correction” formula for limb loss.

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