Study Review

Image from: http://www.webmd.com/diet/ss/slideshow-high-protein-diet

The following is my review of a study published in the June 2002 publication of Obesity Research titled Effect of Protein Intake on Bone Mineralization during Weight Loss: A 6-month Trial by Annebeth R. Skov, Nikolaj Haulrik, Søren Toubro, Christian Mølgaard, and Arne Astrup. According to Wiley Online Library this article was first published online on September 6, 2012.

Introduction

The purpose of this study was to analyze the long-term effects of dietary protein on bone mineralization. Osteoporotic fractures are an increasing problem with serious implications in health. Low protein intake in the elderly is a problem that can lead to an increase in low bone quality. With the prevalence of obesity increasing, despite the fact that a larger body mass tends to increase bone mineralization, weight loss to prevent the ill effects of comorbidities associated with obesity is generally the desired outcome. The often advised dietary recommendations are for a low fat, high complex carbohydrate diet. However, due to the longer satiation effects of protein, a low fat, high protein diet could possibly reduce excess calorie consumption due to frequent bouts of hunger on a lower protein diet. Nonetheless, it has been claimed that protein from animal sources reduces bone mineral content, in addition to the bone mineral losses seen in weight loss. The authors therefore found that it was relevant to study the influences of reduced-fat diets with high and low protein content on bone mineralization in overweight and obese subjects.

Methods

The study involved sixty-five overweight or obese individuals in a 6-month randomized, placebo-controlled dietary-intervention. It compared two controlled diets with isocaloric fat content (30%), one with high protein (25%) and one with low protein content (12%).

Results

The study found that there was no significant difference in BMC loss between the high protein or the low protein groups. However, they noted a more positive correlation between body fat loss and BMC loss than with body weight loss. At the end of 6 months, after adjusting for the differences in fat loss, there was a greater loss of BMC in the low protein group compared of the high protein group. The study found that independent of weight loss, there was less BMC loss with a high protein diet.

Commentary

Overall I agree with the findings of this study. The issues I have are with the diets. In Table 2 the carbohydrate content increased in both diet from baseline to 6 months. Also, the calcium and vitamin D intake for the low protein group decreased while in the high protein group they increased. I am unsure if this is due to the change in macro-nutrients (increased or decreased protein from baseline). That alone could have greatly contributed to the higher rate of BMC loss in the low protein group. It would be beneficial in a future study if not only the fat content were kept the same between groups, but all other micro- and macro-nutrient levels be kept at about the same level as baseline, if possible.

Skov, A. R., Haulrik, N., Toubro, S., Mølgaard, C., &Astrup, A. (2002, June). Effect of Protein Intake on Bone Mineralization duringWeight Loss: A 6-Month Trial. Obesity Research, 10(6), 432-438.doi:10.1038/oby.2002.60