No differences in the body fat after violating core bioelectrical impedance measurement assumptions.

OBJECTIVE: It is unclear to what degree acutely violating bioelectrical impedance analysis (BIA) measurement assumptions will alter the predicted percent fat mass (%FM) and whether this differs by sex or body mass index (BMI). METHODS: %FM was assessed under control, dehydration, exercise, water, food intake and non-voided bladder conditions with three BIA devices (Tanita: BC-418, TBF-314, & Omron HBF-306CN) for men (n = 23, age: 24.0 ± 5.2 years old) and women (n = 17, age: 22.5 ± 3.4 years old) separately. RESULTS: For all BIA devices, there were no differences in the %FM values between the control and the other conditions in men or women (- 1.9 to 0.4%, p > 0.05). Across the three devices and five conditions, 97% of %FM tests returned values within 5% of control (2 tests), and 86% of tests were within 2% of control despite violating an assumption. The errors were greatest with dehydration and women were more likely to have a %FM difference greater than 2% than men with dehydration using the hand-to-foot device (Tanita TBF-314: 59% versus 9%). There were no differences in %FM between control and the conditions when examined by BMI (overweight/obesity: - 2.8 to 0.1% and normal weight: - 1.7 to 0.5%; BMI*trial, p = 0.99). CONCLUSION: %FM estimates were similar despite acutely violating the preliminary measurement BIA assumptions across a range of different BMIs. The minor variations in %FM are smaller than what would be expected with day-to-day variability or weight loss intervention but may be larger in women than men.

Lifestyle and weight predictors of a healthy overweight profile over a 20-year follow-up.

OBJECTIVE: To examine whether changes in modifiable risk factors [physical activity, cardiorespiratory fitness (CRF), body weight, and diet composition] are associated with the transition to metabolically healthy overweight/obese (MHOW) versus metabolically abnormal overweight/obese. METHODS: Analysis included 1,358 adults [aged 25.0 (3.5) years] from the CARDIA study who were healthy at baseline and had overweight/obesity at follow-up. Participants with zero or one of the following six risk factors were classified as MHOW: elevated triglycerides, LDL, blood pressure, fasting glucose, and HOMA-insulin resistance and low HDL. RESULTS: Over the 20-year follow-up, the sample gained weight (BMI 24.5 to 31.1 kg/m(2) ), and the prevalence of MHOW was 47% at follow-up. After adjusting for changes in CRF, diet, and weight change, physical activity and macronutrient intake were not independently associated with MHOW (P > 0.05), while changes in CRF [fit-unfit: RR (95%) = 0.58, 0.52-0.66; unfit-unfit: RR = 0.67, 0.58-0.76, versus fit-fit] and weight [gain: RR (95%) = 0.54, 0.43-0.67; cycle: RR = 0.74, 0.57-0.94, versus stable] were independently associated with MHOW. CONCLUSIONS: Focusing on high CRF and strategies to limit weight gain may be important for individuals with overweight and obesity in early to mid-adulthood to maintain a metabolically healthy profile.