The effect of advice to walk 2000 extra steps daily on food intake.

BACKGROUND: It is currently unclear how physical activity and diet interact within the ranges of activity seen in the general population. This study aimed to establish whether a small, acute, increase in physical activity would lead to compensatory change in energy intake and nutrient balance, and to provide power analysis data for future research in this field.
METHOD: Twelve participants were studied over 7 days of habitual activity and 2 weeks after instruction to increase physical activity by 2000 steps per day. Physical activity was assessed using a diary, the 'activPAL' activity monitor and a pedometer. Dietary analyses from prospective food diaries were compared between the first and third weeks.
RESULTS: Participants increased step-counts (+2600 steps per day, P = 0.008) and estimated energy expenditure (+300-1000 kJ day(-1), P = 0.002) but did not significantly change their energy intake, dietary composition or number of meals per day. From reverse power analysis 38 participants would be needed to exclude a change in energy intake of 400 kJ day(-1) with 90% power at P < 0.05; 400 kJ day(-1) would compensate for a 2000 steps per day increase in physical activity.
CONCLUSION: These results did not demonstrate any compensatory increase in food consumption when physical activity was increased by walking an average of 2600 additional steps per day. Power analysis indicates that a larger study (n = 38) will be necessary to exclude such an effect with confidence.