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Energy expenditure, respiratory exchange ratio, and fat utilization during sub‐maximal exercise in overweight adults adhering to the Atkins or Zone diet
Author(s) -
White Andi,
Johnston Carol S,
Swan Pamela D,
Tjonn Sherrie L
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a582-a
Subject(s) - respiratory exchange ratio , overweight , medicine , carbohydrate , zoology , endocrinology , energy expenditure , analysis of variance , vo2 max , obesity , heart rate , biology , blood pressure
The Atkins diet (AD) and Zone diet (ZD) are high‐protein, low‐carbohydrate diets. AD promotes severe carbohydrate restriction (<20g/d initially) and high‐fat; whereas ZD is moderate in carbohydrate and low‐fat (<30% energy). To examine the AD claim that severe restriction of dietary carbohydrate and ketosis promotes lipid utilization and increased energy expenditure (EE), we randomized 20 healthy overweight adults to six weeks of strictly controlled AD or ZD. The subjects performed a 90‐min walk at 50% maximal oxygen consumption at trial weeks 0, 2, and 6. EE, the respiratory exchange ratio (RER), and the rating of perceived exertion (RPE) were recorded at 10 minute intervals during exercise. Multiple analyses of variance for repeated measures, with time and diet group as factors, were used to assess differences in the data at steady‐state (i.e., at 70 minutes of exercise). EE showed a significant time effect only: in AD, EE was 5% lower at week 6 versus week 0 (p=0.073), but in ZD, EE was not altered over time. Energy utilized from fat also showed a significant time effect (p=0.022): ZD utilized more energy from fat at week 2 versus week 0 (p=0.006), but there was no time effect for AD. A significant time effect was noted for RER (p=0.001): in ZD, RER was lower at week 2 versus week 0 (0.738 and 0.810, respectively, p=0.001) and at week 6 versus week 0 (0.770 and 0.810, respectively, p=0.086). RER did not change during the 6‐wk trial period in AD. There was no significant change in RPE by time or diet group during the trial. These data indicate that the severe carbohydrate restriction and ketosis of AD offered no metabolic advantage in terms of lipid utilization or total EE. Funding source: Inflammation Research Foundation.