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Title

 Normal Protein Intake Is Required for Body Weight Loss and Weight Maintenance, and Elevated protein Intake for Additional Preservation of Resting Energy Expenditure and Fat Free Mass

 

by Soene, Martens, Hochstenbach-Waelen, Lemmens,  and Westerterp-Plantenga

published 2013 in Journal of Nutrition

Introduction

Beneficial conditions for weight loss includes increased satiety, negative energy balance, and sparing of fat free mass, which allows for maintained basal energy expenditure. It is believed that energy restricted diets that have high protein content compared with current standard dietary guidelines are more beneficial for weight loss because they allow the maintenance of fat free mass.

Researchers note that care should be taken when comparing diets that have different total energy levels as the conventional method of assessing macronutrients to analyze relative proportions of energy that come from protein, fat, and carbohydrates. Energy restricted diets reduce total energy levels of the diet so an absolute measure of the protein in the diet is helpful

Researchers wanted to investigate the effects of dietary protein content on weight loss and then on bodyweight maintenance thereafter and body composition during a 6 month energy restricted diet.

Methods

Researchers begun with deciding to look at absolute protein levels at the level of the standard current dietary guidelines which is 0.8 g per kg of bodyweight per day and at a higher guideline of 1.2 g per kg of bodyweight per day. Researchers recruited 80 overweight or obese subjects yet only 72 finished the study. Researchers divided the subjects into two groups. One group ate the high protein diet and the other group ate the standard guideline level protein diet.

Energy intakes for the two groups over the 6 month period were structured as follows: 2 weeks of %100 of maintenance energy requirements, 6 weeks of 33% of original maintenance energy requirements, and 17 weeks of 67% of original maintenance energy requirements. Protein levels for each participants were calculated based on absolute bodyweight and not adjusted to overall macronutrient ratios. The subjects protein sources were man made meal replacements. The protein to carbohydrate to fat ratio of the two groups over the 6 month period were as follows: 10:50:40 and 20:50:30 in first 2 weeks, 30:35:35 and 60:35:5 in the following 6 weeks, and 15:45:40 and 30:45:25 in the last 17 weeks. Researchers also advised subjects to eat 4 portions of fruits and vegetables each day along with 1.5 L of water.

Researchers took measurements at the start and end of each change in energy requirement levels. These measurements included urinary nitrogen, anthropometry, body composition, energy expenditure, eating behavior, physical activity, physiological profiles, and appetite profiles.

Results

Researchers reported that BMI, bodyweight, and waist-to-hip circumference ratio reduced in both groups and no significant differences were reported between groups. Higher protein diet group lost 5.0 kg in 6 week weight loss phase and lower protein diet group lost 5.9 kg. In the 17 week maintenance phase higher protein group lost 2.0 kg and lower protein diet group lost 1.3 kg.

Researchers stated that fat free mass reduced significantly in both groups. The lower protein group lost more fat free mass than the high protein group. Lower protein group lost 1.3 kg of fat free mass in 6 week phase and gained 0.5 kg during 17 week phase. Higher protein group lost 0.6 kg of fat free mass during 6 week phase and gained 0.5 kg of fat free mass in 17 week phase. Researchers noted that the lower protein group had an increased reduction in resting energy expenditure.

Researchers reported that creatinine concentrations did not differ between groups and creatinine concentrations did not change significantly over time in either group.

Conclusion

Researchers ended by concluding that not enough protein content in the diet contributed to the risk of bodyweight regain. Researchers also concluded that higher protein diet of 1.2 g per kg of bodyweight preserves fat free mass better than a diet of 0.8 g per kg of bodyweight.

Take-Away

This study again reaffirms and reminds us that high protein diets are much more effective as the basis for weight loss and fat loss nutritional approaches as it preserves fat free mass and prevents adaptive thermogensis all while allowing for a caloric deficit to be achieved to facilitate weight loss.

References

Strength and Conditioning Research Review. Breadsley, Chris and Contreras, Bret. 2013, May.

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