A
recent study published in the British Medical Journal has received an enormous
amount of publicity. In a well-designed protocol, investigators studied the
effect of a low carbohydrate diet on energy expenditure. Traditional thinking
is a calorie is a calorie whether it comes from protein, fat or carbohydrate.
The researchers found, however, that subjects consuming a low carbohydrate diet
burned significantly more calories per day.
The objective of the study was to test the carbohydrate-insulin model of
obesity. In this model high carbohydrate intake stimulates insulin release
which results in greater fat storage leading to obesity. To test the hypothesis
subjects, following a weight loss period in which they lost 12% of their body
weight, the subjects were assigned to one of three diets for 20 weeks:
- 20% Carb, 20% Protein, 60% Fat
- 40% Carb, 20% Protein, 40% Fat
- 60% Carb, 20% Protein, 20% Fat
Subjects
on the low carb diet burned on average 209 calories more per day than those on
the high carb diet. According to the researchers this metabolic effect may
improve the effectiveness of obesity treatment. However there are lots of
cautions with this study.
The study subjects had their
meals prepared, individual energy measurements were made repeatedly and there
was intense monitoring of the subjects by the research team. In other words
this was not an approach for someone trying to lose weight. Even the
investigators concluded the protocol was too costly and complicated to be
practical. Also there are some other issues that could have influenced the
results. For example, the low carb subjects consumed a high fat diet. Fat
stimulates the release of satiety proteins which affects food consumption.
There also could be issues with patient compliance.
In spite of these limitations
the study results are extremely provocative and provide additional insight on
whether macro-nutrients are metabolized differently. This should not be a
surprise to endurance athletes and in next week's tip, I'll review the
implications of this study on endurance performance.
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