High-Protein Diet Promotes Fat Loss?

Regular readers of these pages are well aware of the importance I attribute to maintaining adequate protein intake especially with a caloric restricted diet.

But how much protein is enough?

This question was addressed by Leo Treyzon and colleagues from the UCLA, Los Angeles, in a controlled trial of protein enrichment of meal replacements for weight reduction just published in the Journal of Nutrition.

This single blind, placebo-controlled, randomized outpatient weight loss trial in 100 obese men and women comparing two isocaloric meal plans utilizing a standard meal replacement (MR) to which was added supplementary protein or carbohydrate powder. MR was used twice daily (one meal, one snack). One additional meal was included in the meal plan designed to achieve individualized protein intakes of either

1) 2.2 g protein/kg of lean body mass (LBM) per day [high protein diet (HP)]

2) 1.1 g protein/kg LBM/day [standard protein diet (SP)].

LBM was determined using bioelectrical impedance analysis (BIA). Body weight, body composition, and lipid profiles were measured at baseline and 12 weeks.

Eighty-five subjects completed the study and weight loss at 12 weeks was similar between the groups (-4.19 kg for HP and -3.72 kg for SP). However, subjects in the HP group lost significantly more fat weight (around 1 Kg) than the SP group as estimated by BIA. The HP group also showed a significant decrease in cholesterol and LDL cholesterol

The authors conclude that a higher protein MR within a higher protein diet results in significantly more fat loss than standard protein intake.

What does this mean? Of course, there are important limitations – a 12 Week study is hardly long enough to determine the long-term success of this high-protein strategy. As with any weight loss strategy, weight loss maintenance requires staying on the regimen – wether or not this would be feasible or acceptable is not a question that this study was designed to answer.

My take home message is that a relatively high-protein diet, if anything, is at least not detrimental to the weight loss process. On the other hand, why this should lead to selective increased loss of fat is not clear to me – but if true – certainly not something anyone would object to.

Toronto, Alberta