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LETTER |
Senior Science Editor
Advanced Research Press, Inc.
Oulu, Finland
E-mail: sportsnutrition{at}luukku.com
Advances are made by answering questions.Discoveries are made by questioning answers.
—Bernard Haisch
The recent review by Johnston published in the Journal suggested, quite incorrectly, that the success of low-carbohydrate/high-protein diets may simply reflect increased thermogenesis and greater satiety afforded by higher intakes of protein rather than the low-carbohydrate nature of the diets [1]. However, the author did not provide any evidence supporting this contention. Indeed, it is becoming increasingly clear that low-carbohydrate diets provide a "metabolic advantage", i.e., induce greater fat loss compared to isocaloric high-carbohydrate/moderate-carbohydrate diets [2–4], and this advantage does not simply relate to dietary protein-induced thermogenesis. In fact, there is some evidence suggesting that calorie content may not be as predictive of fat loss as is reduced carbohydrate consumption [3]. Contrary to what some believe, the "metabolic advantage" certainly does not violate the first law of thermodynamics [3,4]. Recently, Volek et al. encouraged a more unbiased, balanced appraisal of low-carbohydrate diets [5]. To look at the evidence and go away unconvinced is one thing. To not look at the evidence and be convinced against it nonetheless is another.
REFERENCES
Professor
Arizona State University
Mesa, Arizona
E-mail: carol.johnston{at}asu.edu
I appreciate Manninen’s comment on my article describing strategies for healthy weight loss. In fact, I agree that high-protein, low-carbohydrate diets may provide a ‘metabolic advantage’. In my view, the greater thermogenesis afforded by these diets [1] is a ‘metabolic advantage’ and consistent with Manninen’s argument that a calorie is not ‘a calorie’ [2]. In this dialogue Manninen states that amino acid metabolism requires more energy for the body to process than other macronutrients due to the obligatory disposal of nitrogen as urea, and that the turnover of body protein is an energy-dependent process [2], the same arguments that I have used [1,3]. Moreover, the metabolic cost of protein metabolism post-meal is the basis of protein-induced thermogenesis [4]. Interestingly, the satiety afforded by high-protein, low-carbohydrate diets has also been related to protein-induced thermogenesis [5]; hence, this phenomenon may also be considered a component of the ‘metabolic advantage’ of these diets.
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