Conducted by researchers at the Department of Health and Exercise Science, University Of Oklahoma, USA, the study examined physiological response of participants to an exercise program combined with daily supplementation with a commercially-available high-protein/low-carbohydrate and low-fat, nutrient-dense food supplement.
According to their findings, after ten weeks of supplementation, the group of overweight volunteers had "significantly decreased total energy, carbohydrate and fat intake", as well as increased protein and fiber intake.
Previous studies have already shown that high-protein/reduced-carbohydrate and reduced-fat diets have had a beneficial effect on body composition in sedentary, overweight people - either alone or in combination with an energy restricted diet.
The current study, said the researchers, was designed to instead examine the physiological response to supplementation and exercise.
The study recruited 60 overweight men and women, who were divided into three groups.
One group was assigned to ten weeks of exercise, the other undertook exercise and supplementation for the period, while the third was a control group.
After the testing period, the supplemented group was found to have a 14 per cent decrease in total energy intake, a 27 per cent decrease in carbohydrate intake, and a 27 per cent decrease in fat intake.
Protein and fiber intake increased 52 and 21 per cent respectively.
Both the supplemented group and the exercise group were found to have decreased fat mass (9 per cent and 5 per cent respectively).
Total cholesterol and LDL decreased only in the supplemented group, by 12 per cent and 13 per cent respectively.
Total cholesterol-to-HDL ration, however, decreased "significantly" in both exercise groups, said the researchers.
"Absent energy restriction or other dietary controls, provision of a high-protein/low-carbohydrate and -fat, nutrient-dense food supplement significantly, 1) modified ad libitum macronutrient and energy intake (behavior effect), 2) improved physiological adaptations to exercise (metabolic advantage), and 3) reduced the variability of individual responses for fat mass, muscle mass and time-to-exhaustion - all three variables improving in 100% of [supplemented] subjects," wrote the researchers.
The researchers said the reduction in total energy intake may be explained by the satiating effect of protein and/or fiber, although they added that the "modest increase" (+4 g/d) in dietary fiber, albeit statistically significant, was not a major contributing factor.
Instead, they said, the observed non-significant increase in protein, during weeks on to two, and the significant decrease in carbohydrate, fat and energy intake over that same time period in the supplemented group may indicate that carbohydrate or fat reduction spontaneously reduce energy consumption.
Source: Nutrition & Metabolism 2008, 5:11doi:10.1186/1743-7075-5-11 Minimal nutrition intervention with high-protein/low-carbohydrate and low-fat, nutrient-dense food supplement improves body composition and exercise benefits in overweight adults: A randomized controlled trial Authors: Christopher M Lockwood, Jordan R Moon, Sarah E Tobkin, Ashley A Walter, Abbie E Smith, Vincent J Dalbo, Joel T Cramer and Jeffrey R Stout, Metabolic and Body Composition Research Laboratory, Department of Health and Exercise Science, University Of Oklahoma.