Body mass index and waist circumference cutoffs to define obesity in indigenous New Zealanders.

BACKGROUND: The suggestion that body mass index (BMI) cutoffs to define obesity should differ in persons of Polynesian descent compared with Europeans is based principally on the observation that persons of Polynesian descent have a relatively higher proportion of lean body mass for a given BMI. OBJECTIVES: The objectives were to determine whether the relation between BMI, waist circumference, and metabolic comorbidity differs in the 2 major ethnic groups in New Zealand and to ascertain whether ethnicity-specific BMI and waist circumference cutoffs for obesity are justified for Maori (indigenous New Zealanders). DESIGN: Subjects included a convenience sample of 1539 men and women aged 17-82 y (47% Maori, 53% white) with measures of BMI, waist circumference, blood pressure, fasting insulin, glucose, and lipids. The sensitivity and specificity of BMI (in kg/m(2); 30 and 32), waist circumference (80 and 88 cm in women, 94 and 102 cm in men), and waist-to-height ratio (WHtR; > or =0.6) in relation to insulin sensitivity, insulin resistance, and the metabolic syndrome were determined. Receiver operating characteristic curves and areas under the curve (AUCs) were also calculated. RESULTS: No ethnic or sex differences between AUCs were observed for BMI, waist circumference, or WHtR, which showed that these anthropometric measures perform similarly in Maori and European men and women and correctly discriminate between those with and without insulin resistance or the metabolic syndrome 79-87% of the time. Any increase in specificity from a higher BMI cutoff of 32 in Maori was offset by appreciable reductions in sensitivity. CONCLUSION: These findings argue against having different BMI or waist circumference cutoffs for people of Polynesian descent.

Determining optimal approaches for weight maintenance: a randomized controlled trial.

BACKGROUND: Weight regain often occurs after weight loss in overweight individuals. We aimed to compare the effectiveness of 2 support programs and 2 diets of different macronutrient compositions intended to facilitate long-term weight maintenance. METHODS: Using a 2 x 2 factorial design, we randomly assigned 200 women who had lost 5% or more of their initial body weight to an intensive support program (implemented by nutrition and activity specialists) or to an inexpensive nurse-led program (involving "weigh-ins" and encouragement) that included advice about high-carbohydrate diets or relatively high-monounsaturated-fat diets. RESULTS: In total, 174 (87%) participants were followed-up for 2 years. The average weight loss (about 2 kg) did not differ between those in the support programs (0.1 kg, 95% confidence interval [CI] -1.8 to 1.9, p = 0.95) or diets (0.7 kg, 95% CI -1.1 to 2.4, p = 0.46). Total and low-density lipoprotein (LDL) cholesterol levels were significantly higher among those on the high-monounsaturated-fat diet (total cholesterol: 0.17 mmol/L, 95% CI 0.01 to 0.33; p = 0.040; LDL cholesterol: 0.16 mmol/L, 95% CI 0.01 to 0.31; p = 0.039) than among those on the high-carbohydrate diet. Those on the high-monounsaturated-fat diet also had significantly higher intakes of total fat (5% total energy, 95% CI 3% to 6%, p < 0.001) and saturated fat (2% total energy, 95% CI 1% to 2%, p < 0.001). All of the other clinical and laboratory measures were similar among those in the support programs and diets. INTERPRETATION: A relatively inexpensive program involving nurse support is as effective as a more resource-intensive program for weight maintenance over a 2-year period. Diets of different macronutrient composition produced comparable beneficial effects in terms of weight loss maintenance.

Sustainability of lifestyle changes following an intensive lifestyle intervention in insulin resistant adults: Follow-up at 2-years.

The objective of this study was to determine whether overweight insulin resistant individuals who lost weight and improved cardiovascular risk factors during a 4-month lifestyle intervention could sustain these lifestyle changes in the long-term. Seventy-nine insulin resistant adults were randomised to a control group or either a modest or intensive lifestyle intervention group for 4-months. Thereafter the two intervention groups were combined and all participants were followed-up at 8, 12 and 24 months. Anthropometry, blood pressure, fasting glucose, lipids, insulin and aerobic fitness were measured and dietary intake was assessed. An interview was conducted to determine factors which participants perceived facilitated or hindered maintenance of healthy lifestyle habits. Seventy-two (91.1%), sixty-nine (87.3%) and sixty-two (78.5%) participants were retained at 8, 12 and 24-month respectively. At 4-months the adjusted difference in weight between the modest and control groups was -3.4 kg (95% CI -5.4, -1.3) p=0.002 and intensive and control groups was -4.7 kg (-6.9, -2.4) p=0.0001 respectively. At 2-years there were no significant differences for weight when the initial 3 groups were compared or when the combined intervention group was compared with the control group. At 2-years, 64% of participants reported that more frequent follow-up would have helped them to maintain healthy lifestyle habits. Even intensive counselling for 4-months with 4-monthly and then yearly monitoring were not enough for maintaining lifestyle changes sufficient to sustain weight loss. More frequent monitoring for an indefinite period was perceived by two-thirds of participants as necessary for them to maintain their initial lifestyle changes.