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Background and aims: Decreasing energy intake relative to energy expenditure is the indisputable tenet of weight loss. In addition to caloric restriction modification of the type of dietary fat may provide further benefits. The aim of the present study was to examine the effect of energy restriction alone and with dietary fat modification on weight loss and adiposity, as well as on risk factors for obesity related disease. Methods and results: One-hundred and fifty overweight men and women were randomized into a 3 month controlled trial with four low fat (30% energy) dietary arms: (1) isocaloric (LF); (2) isocaloric with 10% polyunsaturated fatty acids (LF-PUFA); (3) low calorie (LF-LC) (2 MJ); (4) low calorie with 10% PUFA (LF-PUFA-LC). Primary outcomes were changes in body weight and body fat and secondary outcomes were changes in fasting levels of leptin, insulin, glucose, lipids and erythrocyte fatty acids. Changes in dietary intake were assessed using 3 day food records. One-hundred and twenty-two participants entered the study and 95 completed the study. All groups lost weight and body fat (P < 0.0001 time effect for both), but the LC groups lost more weight (P Z 0.026 for diet effect). All groups reduced total cholesterol levels (P < 0.0001 time effect and PZ 0.017 intervention effect), but the LC and PUFA groups were better at reducing triacylglycerol levels (PZ 0.056 diet effect). HDL increased with LF-LC and LF-PUFA but not with LF-PUFA-LC (0.042 diet effect). The LF and LF-LC groups reported greater dietary fat reductions than the two PUFA groups (PZ 0.043). Conclusion: Energy restriction has the most potent effect on weight loss and lipids, but fat modification is also beneficial when energy restriction is more modest.

Background/Objectives: Most dietary interventions have metabolic effects in the short term, but long-term effects may require dietary fat changes to influence body composition and insulin action. This study assessed the effect of sustained high polyunsaturated fatty acids (PUFA) intake through walnut consumption on metabolic outcomes in type II diabetes.Subjects/Methods: Fifty overweight adults with non-insulin-treated diabetes (mean age 54±8.7 years) were randomized to receive low-fat dietary advice ±30 g per day walnuts targeting weight maintenance (around 2000 kcal, 30% fat) for 1 year. Differences between groups were assessed by changes in anthropometric values (body weight, body fat, visceral adipose tissue) and clinical indicators of diabetes over treatment time using the general linear model.Results: The walnut group consumed significantly more PUFA than the control (P=0.035), an outcome attributed to walnut consumption (contributing 67% dietary PUFA at 12 months). Most of the effects were seen in the first 3 months. Despite being on weight maintenance diets, both groups sustained a 1-2 kg weight loss, with no difference between groups (P=0.680). Both groups showed improvements in all clinical parameters with significant time effects (P

Overweight and obesity are highly significant public health concerns because of the close association of the metabolic syndrome with chronic and potentially fatal diseases (WHO, 2002). The prevalence rates of overweight and obesity have substantially increased over the past decade and arecurrently the highest on record (Yanovski and Yanovski, 2002). Developed countries exhibit higher prevalence rates; however, the difference between developed and developing countries is gradually becoming less evident. In Australia 62% of men and 45% of women are classified as being overweight or obese based on their body mass index (BMI) score (Australian Bureau of Statistics, 2006). Abdominal obesity has been shown to be associated with an increased risk of developing chronic diseases compared to general obesity, where fat is distributed more evenly around the body (Summers et al., 2002). The diseases most commonly associated with abdominal obesity are hypertension, dislipidaemia, type 2 diabetes mellitus, cardiovascular disease and certain types of cancer (Expert panel on the identification evaluation and treatment of overweight in adults, 1998). Worldwide efforts are being made to combat rising obesity rates, with the aim to develop effective treatment and intervention techniques (Swinburn, 2002).