The respondents were classified into three groups based on a classification that broadly followed the current national recommendations for physical activity: inactive, moderately active and vigorously active.
4 The covariates included in the regression analyses were age, gender, physical activity (active, moderately active, and inactive), BMI level (normal-weight, underweight, overweight, and obese), personal income, and smoking status (current, former or never smoker).
Three activity levels active, moderately active, and inactive were based on the calculation of total daily energy expenditure from the duration and frequency of the respondents' leisure time and transportation activities.
Briefly, overall physical activity was assessed from three questions referring to the past year and an index was derived by allocating individuals to four categories of overall activity (inactive, moderately inactive, moderately active and active) [ 17].
Model 2 was additionally adjusted for the following potential lifestyle confounders: educational level (none, primary school, technical/professional, secondary school, higher education); physical activity (inactive, moderately inactive, moderately active, and active); smoking status (never, former, and current); BMI (kilograms per square meter); and alcohol intake (grams per day).
In a study of 288 498 participants in the European Prospective Investigation into Cancer and Nutrition which included baseline self-reporting of activity (inactive, moderately inactive, moderately active and active categories) plus baseline and follow-up objective measurement of weight and waist circumference, physical activity had no relationship with subsequent weight.
Multivariable model 2 adjusted for physical activity (inactive, moderately inactive, moderately active and active) and educational level (none, GCSE (completed to age 15 years), A Level (completed to age 17 years) and degree level) in addition to the adjustments in multivariable model 1.
Next, we added known diabetes risk factors to the model, including BMI (continuous), smoking status (current, former, and never), alcohol consumption (≤10, 11 24, and ≥25 g/day), education level (none, primary school completed, technical or professional school, secondary school, and longer education), and physical activity (inactive, moderately inactive, moderately active, and active).
Model 2 included further adjustment for physical activity (classified into 'inactive'moderatelyely inactive'moderatelyely active' and 'active' according to the validated Cambridge Physical Activity Index [ 35]), smoking status (never, former, current), educational level (none, primary, technical/professional, secondary, university) and total energy intake (continuous).
A TPA index with four activity levels was constructed: 'sedentary'minimallylly active'moderatelyely active', and 'very active'.
Children in the middle tertile ('moderately active) and higher active groups had significantly lower increases in FMI than those in low active group (p's<0.01).
