Abstract
Statement of Problem
Low carbohydrate diets such as the Atkins diet induce weight loss but the combined effects of decreased mood, increased fatigue, increased perception of effort and reduced capacity to exercise may alter submaximal and high intensity exercise responses. The purpose was to evaluate the effects of the Atkins dietary intervention on mood state and the physiological responses during submaximal and high intensity exercise.
Methods
Twenty-four healthy males volunteered to participate in the study. All subjects performed a graded exercise test to exhaustion (GXT) on a cycle ergometer or treadmill. Subjects were pair-matched and divided into two groups [control(C) and Atkins (A)]. All subjects kept a daily food record for 9 days and provided 24-hr urine samples on protocol days 3, 6 and 9 for evaluating pH and ketones. On protocol day 3 (baseline), subjects answered the Profile of Mood States (POMS) questionnaire, followed by a 40-minute exercise bout at 58 (± 10.2) % of V02max. Expired gases and RPE were measured at I 0-minute intervals. At 40 minutes, intensity was increased to 90% of VO2max and time-to-exhaustion was recorded. Beginning on protocol day 4, the C group consumed their normal diet and the A group followed the induction phase of the Atkins diet for 6 days. On protocol day 9, POMS questionnaire and baseline exercise tests were repeated.
Results
Daily CHO intake in the A group was reduced from 48% to 9% (p < .05). pH was reduced 9.8% ( P < .05) in the A group at protocol day 9. POMS TMD was increased 768.5% in the A group (p < .05) at protocol day 9. During exercise, fat oxidation increased. RER was reduced by 12.8 % (p < .05) in the A group compared to C. V02 and RPE in the A group were significantly higher than baseline but were not different than the C group. Time-to-fatigue in the A group was also reduced compared to baseline but
not different from C.
Conclusion
The Atkins diet was successful in significantly reducing CHO intake. This had a profound effect on resting urinary markers of ketogenesis and mood. Despite a large shift in substrate utilization during submaximal exercise, there were minimal effects on V02, RPE and time to exhaustion during high intensity exercise. This indicates that a 6-day Atkins dietary intervention has large effects on resting mood with minimal effects during submaximal and high intensity exercise.