Cross-sectional associations between different measures of obesity and muscle strength in men and women in a British cohort study.

OBJECTIVES: The relationship between obesity and grip strength, a key indicator of sarcopenia, has been inconsistently reported. We aimed to examine associations between grip strength and both body mass index (BMI), a clinical indicator of total adiposity, and waist circumference (WC), an indicator of central adiposity.

DESIGN: Cross-sectional study.

SETTING AND PARTICIPANTS: Data collected from 8,441 men and women, aged 48-92 years old, who attended the third health examination of the European Prospective Investigation into Cancer-Norfolk study was used.

MEASUREMENTS: Maximum grip strength (Smedley dynamometer), BMI (weight/height2) and WC (measured at the natural waist) were ascertained at a research clinic. The associations between grip strength and adiposity measures were explored using linear regression with adjustment for age, height, social class, physical activity, prevalent disease, smoking status and alcohol intake.

RESULTS: Men and women were examined separately and those in the upper quartile of BMI were 2.70kg (95%CI 2.07, 3.33) and 1.46kg (95%CI 1.05, 1.86) stronger respectively than those in the bottom quartile (P trends <0.001). Grip strength also increased weakly with increasing WC. However, including both BMI and WC in the same regression model revealed an inverse association between grip strength and WC, whilst the previously observed association with BMI strengthened. For every 10cm increase in WC, grip strength was 3.56kg (95%CI 3.04, 4.08) lower in men and 1.00kg (95%CI 0.74, 1.24) lower in women.

CONCLUSIONS: Larger overall body mass, indicated by higher BMI, is associated with stronger grip strength but high WC, a clinical indicator of central obesity, is associated with lower grip strength. Abdominal fat is the most metabolically active adipose tissue and this provides a clue to potential mechanisms underlying relationships between fat and skeletal muscle. Additionally, it reinforces the recommendation to measure WC in clinical practice, especially when BMI is below obese ranges.