Study Title:

Higher Protein Boosts Fat Burning

Study Abstract

Aim: Fat oxidation is impaired in obesity. The aim of the present study was to determine if fat oxidation, seen in a high-protein meal response, was influenced by body composition.

Methods: Subjects were provided with control (14% protein, glycaemic index, GI 65), high-protein high-GI (33% protein, GI 74) and high-protein low-GI (35% protein, GI 45) meals. Substrate oxidation and energy expenditure were measured in room calorimeters over eight hours in 18 subjects. Results were compared using a repeated-measures anova with a customised post-hoc analysis (to compare the protein diets averaged vs control and to compare the low- and high-GI diets) and covariates in a linear model of the form: y = α + β1 × fat-free mass (kg) + β2 × loge fat mass (kg).

Results: The full model found significant meal effects on fat oxidation (0.21 ± 0.21 kcal/minute high-protein high-GI, 0.34 ± 0.11 kcal/minute high-protein low-GI, 0.55 ± 0.2 kcal/minute control, F = 3.50, P = 0.007). The effect on energy expenditure (1.67 ± 0.07 kcal/minute high-protein high-GI, 1.61 ± 0.08 kcal/minute high-protein low-GI, 1.67 ± 0.08 kcal/minute control) approached significance (F = 2.45, P = 0.070). Post-hoc analysis revealed a protein effect (P = 0.004 for fat oxidation and P = 0.030 for energy expenditure). Significant interactions indicated that meal response was influenced by body composition. The high-protein meals eliminated the negative relationship between body fat and fat oxidation (α = −4.7, β2 = 2.23, P < 0.01) and between body fat and energy expenditure, which were evident in the control meal (α = −1.5, β2 = 0.63, P < 0.05). No effect of GI was evident.

Conclusion: High-protein intakes may ameliorate an obesity-induced decline in fat oxidation.

From press release:

A low kilojoule diet made up of higher protein meals improves the ability to burn fat among overweight and obese people and may be the key to shedding excess kilos, according to new Australian research.

The study, in Nutrition & Dietetics published by Wiley-Blackwell, found higher protein meals may have a subtle fat-burning effect in overweight or obese people. And the study showed the glycaemic index (GI) of a meal has no additional effect on fat breakdown.

Study co-author Dr. Marijka Batterman, an Advanced Accredited Practising Dietitian, said: 'We know from past research that overweight or obese people are not as efficient at burning fat. This new study shows that fat oxidation, or the body's ability to 'burn' fat, improves in obese people when they eat a higher protein diet.'

Study participants were put on two protein-enriched meals and one standard meal, which all contained the same number of kilojoules. The two protein-enriched meals differed in the type of carbohydrate they contained - either high- or low-GI. The amount of kilojoules subjects burnt was then measured.

The high-protein meals led to the greatest level of fat oxidation. This plan included a cheese and tomato omelette for breakfast, and a beef, chutney and salad sandwich, with a tub of low-fat yoghurt, for lunch.

"We found a clear relationship between body composition and the effect of dietary protein on fat oxidation. Our bodies burn energy and use fat differently, and we need to take this into account when planning our diets,' said Dr. Batterman who works at the Smart Foods Centre at the University of Wollongong.

Claire Hewat, Executive Director of the Dietitians Association of Australia (DAA), said all foods could fit into a healthy diet if eaten in the right amounts, and combined with regular physical activity.

'Forget the fad diets that are so fashionable these days. Instead, include lean protein from healthy foods like lean red meat, chicken and fish, legumes, eggs, nuts and reduced-fat dairy foods. People wanting individual advice on how much protein they need should see an Accredited Practising Dietitian,' said Ms Hewat.

Study Information

Marijka BATTERHAM, Rachael CAVANAGH, Arthur JENKINS, Linda TAPSELL, Guy PLASQUI and Peter CLIFTON.
High-protein meals may benefit fat oxidation and energy expenditure in individuals with higher body fat.
Nutrition & Dietetics
2008 November
Smart Foods Centre, School of Health Sciences, and CSIRO Human Nutrition, Adelaide, South Australia, Australia.

Full Study