The Effect of a Low-Fat, High-Protein or
High-Carbohydrate Ad Libitum Diet on Weight Loss
Maintenance and Metabolic Risk Factors
Claessens M, van Baak MA, Monsheimer S, Saris WH
Int J Obes (Lond) 2009 Mar 33(3):296-304

High-protein diets should be considered more often in weight reduction programs.

This randomized clinical trial show that weight maintenance during 12 weeks after a
5-week very-low-energy diet was better in participants eating a high-protein,
moderate-carbohydrate diet, compared to a moderate-protein, high-carbohydrate
diet. The type of protein (fast or slow absorption) did not have an effect on weight
maintenance. The study extends the results, showing a beneficial effect of protein
from the weight loss phase to the period after this phase.

Earlier studies have shown that high-protein diets may induce better weight
reduction compared to high-carbohydrate diets. This effect has been linked to the
satiety effects of protein and to the high metabolic cost of metabolizing protein.
Moreover, preliminary studies have suggested that the type of protein (fast
absorption, such as whey, vs. slow absorption, such as casein) could have an effect
on satiety and perhaps on weight reduction. The diet composition (as % in energy
intake) in the present study was as follows: high-protein, moderate-carbohydrate
diet: protein 35%, carbohydrate 42%, fat 24%; moderate-protein, high-carbohydrate
diet: protein 16%, carbohydrate 63%, fat 21%. Moreover, the high-protein
participants were divided into casein-enriched and whey-enriched groups.

The combined high-protein groups lost about 1kg during the 12-week intervention period,
whereas the high-carbohydrate group gained an approximately equal amount. No
time-by-treatment effect was observed when comparing the two protein groups. The
focus on weight maintenance period after weight loss was the new aspect and
strength in the present study. Moreover, the comparison of two different types of
proteins was new and interesting, despite negative results. The short time frame
was a limitation: future studies should use longer interventions and/or follow the
participants for at least 1 year after the intervention. It would also be important to
compare the long-term effects on weight maintenance of high-protein, moderate
carbohydrate, low-fat diets with high-protein, high-fat, low-carbohydrate diets.
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