Objective: To compare changes over time in waist circumference (a measure of central fatness) and body mass index (a measure of overall obesity) in British youth. Design: Representative cross sectional surveys in 1977, 1987, and 1997. Setting: Great Britain. Participants: Young people aged 11–16 years surveyed in 1977 (boys) and 1987 (girls) for the British Standards Institute (n=3784) and in 1997 (both sexes) for the national diet and nutrition survey (n=776). Main outcome measures: Waist circumference, expressed as a standard deviation score using the first survey as reference, and body mass index (weight(kg)/height(m) ² ), expressed as a standard deviation score against the British 1990 revised reference. Overweight and obesity were defined as the measurement exceeding the 91st and 98th centile, respectively. Results: Waist circumference increased sharply over the period between surveys (mean increases for boys and girls, 6.9 and 6.2 cm, or 0.84 and 1.02 SD score units, P<0.0001). In centile terms, waist circumference increased more in girls than in boys. Increases in body mass index were smaller and similar by sex (means 1.5 and 1.6, or 0.47 and 0.53 SD score units, P<0.0001). Waist circumference in 1997 exceeded the 91st centile in 28% (n=110) of boys and 38% (n=147) of girls (against 9% for both sexes in 1977-87, P<0.0001), whereas 14% (n=54) and 17% (n=68), respectively, exceeded the 98th centile (3% in 1977-87, P<0.0001). The corresponding rates for body mass index in 1997 were 21% (n=80) of boys and 17% (n=67) of girls exceeding the 91st centile (8% and 6% in 1977-87) and 10% (n=39) and 8% (n=32) exceeding the 98th centile (3% and 2% in 1977-87). Conclusions: Trends in waist circumference during the past 10–20 years have greatly exceeded those in body mass index, particularly in girls, showing that body mass index is a poor proxy for central fatness. Body mass index has therefore systematically underestimated the prevalence of obesity in young people. What is already known on this topic: The prevalence of overweight and obesity in youth based on body mass index has increased over the past 10–20 years Body mass index gives no indication of body fat distribution Waist circumference is a marker for central body fat accumulation; a large waist circumference is linked to an increased risk of metabolic complications What this study adds: Waist circumference in British youth has increased over the past 10–20 years at a greater rate than body mass index, the increase being greatest in females The accumulation of central body fat has risen more steeply than whole body fatness based on height and weight Current and future morbidity in British youth may be seriously affected due to accumulation of excess central fat

With energy intake restriction and exercise remaining the key diet and lifestyle approaches to weight loss, this is not without potential negative implications for body composition, metabolic health, and quality and quantity of life. Ideally, weight loss should be derived almost exclusively from the fat mass compartment as this is the main driver of metabolic disease, however, several studies have shown that there is an accompanying loss of tissue from the fat-free compartment, especially skeletal muscle. Population groups including post-menopausal women, the elderly, those with metabolic disease and athletes may be particularly at risk of skeletal muscle loss when following a weight management programme. Research studies that have addressed this issue across a range of population groups are reviewed with a focus upon the contribution of resistance and endurance forms of exercise and a higher intake dietary protein above the current guideline of 0.8 g/kg body weight/day. While findings can be contradictory, overall, the consensus appears that fat-free and skeletal muscle masses can be preserved, albeit to varying degrees by including both forms of exercise (but especially resistance forms) in the weight management intervention. Equally, higher intakes of protein can protect loss of these body compartments, acting either separately or synergistically with exercise. Elderly individuals in particular may benefit most from this approach. Thus, the evidence supports the recommendations for intakes of protein above the current guidelines of 0.8 g/kg body weight/d for the healthy elderly population to also be incorporated into the dietary prescription for weight management in this age group.

OBJECTIVE: To compare waist circumference (a measure of central fatness) and body mass index (BMI, a measure of general fatness) between a contemporary cohort and similar aged British children measured in 1987. DESIGN: Comparative study of two cohorts. The first was a cross-sectional survey and the second an ongoing longitudinal survey. SETTING: The cross-sectional study was conducted throughout Great Britain during 1987. The ongoing longitudinal study was conducted in the Avon region between 1995 and 1998. PARTICIPANTS: A total of 1821 children were measured in the cross-sectional study, and around 1000 children were measured in the longitudinal study. Ages ranged between 2 and 5 y. MAIN OUTCOME MEASURES: Waist circumference, height, weight and BMI. Values were expressed as mean±s.d. Age-related measures were compared. RESULTS: At equivalent ages, mean waist circumference values were greater in the contemporary children, compared with children measured in the earlier cross-sectional study in 1987 (P<0.05). Although boys from the contemporary cohort had the larger absolute waist circumference measurements, the absolute and percentage differences in waist circumference between the cohorts were greater for the girls. Mean BMI values were slightly but significantly higher in the contemporary children compared with children measured in the earlier cross-sectional study (P<0.05). The proportional increase in waist circumference for each age–sex group generally exceeded the proportional increase in BMI. CONCLUSION: These results suggest that central fatness in young British children has increased over the period of 1987–97 to a greater extent than general fatness. This should be of concern since evidence associates greater central adiposity with adverse levels of cardiovascular risk factors in children. Furthermore, the study highlights important shortcomings of the BMI measurement, in that it provides no information on body fat distribution and can mask true obesity-related risk in children.

The global epidemic of obesity in children will see a rise in the number of cases of metabolic syndrome, which is a clustering of CVD risk factors, including atherogenic levels of blood lipids, hyperinsulinaemia and raised blood pressure. Rather than excess general fatness (assessed by BMI), more specifically it is excess abdominal fatness, quantified by waist circumference measurement, which is a better measure of risk for these metabolic abnormalities in children of all ages. Insulin resistance, a consequence of excess visceral fat, is understood to be the driving force underpinning the metabolic syndrome. Consequently, assessment of abdominal fatness in children is proving to be more clinically useful. Waist circumference centile charts have now been developed for the UK and other paediatric populations to assist in this process. Furthermore, studies in the UK and elsewhere have shown that abdominal fatness has increased in infants, children and adolescents to a greater extent than overall fatness over the past 10–20 years, suggesting that obesity prevalence may be underestimated when based entirely on BMI. Additionally, ethnic differences in fat distribution have been demonstrated in children, with those from south Asian backgrounds having a greater abdominal distribution compared with Caucasian children and consequently having a much greater risk for type 2 diabetes. The information that can be provided by waist circumference measurement in children, as in adults, together with the recent changes in body fat distribution should provide the impetus for its measurement to be standardised and routinely taken in clinical and epidemiological settings.