¹Menzies School of Health Research, Casuarina, Australia

²Nutrition and Dietetics, Department of Medicine, Monash University, Monash Medical Centre, Clayton, Australia

³The Nutrition Department, The Alfred Hospital, Prahran, Australia

⁴Department of Nutrition, Dietetics and Food Science, School of Public Health, Curtin University of Technology, Perth, Australia

Correspondence to: L S Piers, Menzies School of Health Research, PO Box 41096, Casuarina, NT 0811, Australia. E-mail: sunil.piers@menzies.edu.au

Objective: To compare postprandial whole-body fat oxidation rates in humans, following high-fat (43% of total energy) mixed breakfast meals, of fixed energy and macronutrient composition, rich in either monounsaturated fat (MUFA) from extra virgin olive oil or saturated fat (SFA) from cream.

Design: Paired comparison of resting metabolic rate (RMR), thermic effect of a meal and substrate oxidation rates following consumption of isocaloric breakfast meals, differing only in the type of fat, administered in random order 1-2 weeks apart.

Subjects: Fourteen male volunteers, body mass index (BMI) in the range 20-32 kg/m², aged 24-49 y and resident in Melbourne, Australia, were recruited by advertisement in the local media or by personal contact.

Measurements: Body size and composition was determined by anthropometry and dual energy X-ray absorptiometry (DEXA). Indirect calorimetry was used to measure RMR, thermic effect of a meal, post-meal total energy expenditure and substrate oxidation rate. Blood pressure and pulse rates were measured with an automated oscillometric system. Fasting and 2 h postprandial glucose and insulin concentrations and the fasting lipid profile were also determined.

Results: In the 5 h following the MUFA breakfast, there was a significantly greater postprandial fat oxidation rate (3.08±4.58 g/5 h, P=0.017), and lower postprandial carbohydrate oxidation rate (P=0.025), than after the SFA breakfast. Thermic effect of a meal was significantly higher (55 kJ/5 h, P=0.034) after the MUFA breakfast, in subjects with a high waist circumference (HWC99 cm) than those with a low waist circumference (LWC<99 cm). This difference was not detected following the SFA breakfast (P=0.910).

Conclusion: If postprandial fat oxidation rates are higher after high MUFA, rather than SFA meals, then a simple change to the type of dietary fat consumed might have beneficial effects in curbing weight gain in men consuming a relatively high-fat diet. This may be particularly evident in men with a large waist circumference.

International Journal of Obesity (2000) 26, 814-821. doi:10.1038/sj.ijo.0801993

waist circumference; resting metabolic rate; thermic effect of a meal; fat oxidation rate; obesity; human